Methodology
Report #24: Estimation Procedures for the 2007 Medical Expenditure
Panel Survey Household Component
Machlin S.R., Chowdhury S.R., Ezzati-Rice
T., DiGaetano R., Goksel H., Wun L.-M., Yu W., Kashihara D.
Table of Contents
_._ Abstract
1.0 Introduction
1.1 Summary of MEPS Sample Design
1.2 Terms Related to Sampling/Target Population
1.3 MEPS Analytic Files
1.4 Overview of Development of MEPS Weights
2.0 Point-in-Time (PIT) Weights
2.1 Development of Panel-Specific PIT Weights
2.2 Development of Combined-Panel PIT Weights
2.3 General Issues Related to Developing PIT Weights
3.0 Full Year (FY) Weights
3.1 Development of Panel-Specific FY Weights
3.2 Development of Combined-Panel Person Weights for FY Population
Characteristics File
3.3 Development of Final FY Weights for Consolidated File
3.4 General Issues Related to Developing FY Weights
4.0 Weights for Survey Supplements
4.1 Self-Administered Questionnaire (SAQ)
4.2 Diabetes Care Supplement (DCS)
5.0 Longitudinal Weights
6.0 Variance Estimation
7.0 References
Figure 1. Overview of MEPS Household Component Panel Design, 2002–2007
Figure 2. Illustration of MEPS from Longitudinal Perspective, Panel
10 (2006–2007)
Figure 3. Person-Level PIT and FY Weight Development Process
Figure 4. Family-Level PIT and FY Weight Development Process
Figure 5. Pooling of Overlapping MEPS Panels for PIT File
Appendix A. Distribution of Weights at Different Stages of Weighting
for 2007 MEPS
Appendix B. Variables Used in Nonresponse and Poststratification/Raking
Adjustments
Appendix C. Glossary of Selected Terms
Abstract
The primary purpose of this report is to describe the procedures used to develop various MEPS analytic weights. A working knowledge of these procedures is important for researchers who wish to produce accurate and valid national estimates from the MEPS data. Following an introductory section that provides a brief overview of the survey design as well as the types of MEPS analytic files and weight variables, the report provides detailed descriptions of the procedures used to develop the various MEPS analytic weights (Point-in-Time, Full Year, Survey Supplements, and Longitudinal weights). The last section provides an overview of the variance estimation procedures used to analyze MEPS data. Although MEPS weighting procedures do not vary substantially from year to year, the details presented in this report apply specifically to the 2007 data year.
1.0 Introduction
The Medical Expenditure Panel Survey (MEPS) Household Component (HC)
is a nationally representative sample of the U.S. civilian noninstitutionalized
population. Sponsored by the Agency for Healthcare Research and Quality
(AHRQ) of the U.S. Department of Health and Human Services (DHHS), MEPS
has been conducted continuously since 1996. MEPS provides comprehensive
data on health care use, expenditures, sources of payment, and health
insurance coverage as well as information on survey respondents' health
status, demographic/socio-economic characteristics, employment status,
access to health care, and satisfaction with health care. Estimates can
be produced for persons and families in the U.S. as well as subgroups
of the population.
Because MEPS is a complex probability sample, analytic approaches
based on data from a simple random sample are usually not appropriate.
In particular, ignoring the complex design can lead to biased estimates
and inaccurate significance levels. Sample weights and the stratification
and clustering aspects of the design must be incorporated into analyses
in order to produce appropriate estimates and standard errors of estimates.
The primary purposes of this report are to describe the procedures
used to develop the various MEPS analytic weights and provide an overview
of appropriate variance estimation procedures. A working knowledge
of this information is important for researchers who wish to produce
accurate, valid national estimates from the MEPS data. In this introduction,
we provide a brief overview of the survey design as well as the types
of MEPS analytic files and weighting variables. Sections 2–6
provide detailed descriptions of the procedures used to develop the
various MEPS analytic weights while Section 7 provides an overview
of the main variance estimation procedures used to analyze MEPS data.
MEPS weighting procedures do not generally change substantially over
time but there can be minor differences in implementation from year
to year. The details presented in this report apply specifically to
the 2007 data year. A glossary of various terms used in this report
that have a technical definition for MEPS can be found in Appendix
C.
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1.1 Summary of MEPS Sample Design
The MEPS-HC is a complex national
probability sample survey of the U.S. civilian noninstitutionalized
population. Each year a new sample of households is selected from among
those households that participated in the previous year’s National
Health Interview Survey (NHIS), another large ongoing federal health
survey conducted by the National Center for Health Statistics (NCHS)
of the Centers for Disease Control and Prevention (CDC). The NHIS is
based on a probability sample of the U.S. civilian noninstitutionalized
population selected through a complex multistage area sample design.
The details of the NHIS sample design can be found in Botman et al.
(2000). The MEPS sample of households is a subsample of NHIS responding
households and reflects many of the features of the NHIS design. Ezzati-Rice
et al. (2008) provides some details of the common features of the NHIS
and MEPS designs.
Each new MEPS sample is referred to as a panel and data for each panel
are collected through a series of five rounds of computer-assisted
personal interviews (CAPI) that yield annual data for each of two consecutive
calendar years. The first two interviews (Rounds 1–2) cover most
of the first year, the last two interviews (Rounds 4–5) cover
most of the second year, and the middle interview (Round 3) covers
the end part of the first year and the beginning part of the second
year.
A new MEPS panel of households has been selected and fielded every
year since 1996. As illustrated in Figure 1 for 2002–2007, data
are combined across two distinct nationally representative samples,
making use of the MEPS overlapping panel design to increase the precision
of annual estimates produced from MEPS.1 More specifically, annual
estimates are made by combining data from two consecutive panels—one
from the first year of data collection and the other from the second
year
of data collection. For example, 2007 annual estimates are based on
data collected for the second year of Panel 11 and data collected for
the first year of Panel 12.
Figure 1. Overview of MEPS Household Component Overlapping
Panel Design, 2002–2007
In addition to annual estimates, the MEPS design structure permits
longitudinal estimates over two consecutive calendar years, thus allowing
examination of person-level changes in selected variables over a two
year period for a single panel. For example, research analysts can
assess the persistence of high health care expenditures by examining
whether individuals with high expenditures in one year also have high
expenditures in the subsequent year or shift to a lower expenditure
level. Figure 2 provides an illustration of MEPS from a longitudinal
perspective for Panel 11. Data for this panel can be used to analyze
person-level changes in round-specific variables or changes in annual
level variables (e.g., total health care expenditures) between 2006
and 2007.
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Figure 2. Illustration of MEPS from Longitudinal Perspective,
Panel 10 (2006–2007)
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1.2 Terms Related to Sampling/Target Population
The terms “RU,” “in-scope,” “Key,” and “eligible” are
used at times in this report in the context of developing analytic
weights for MEPS sample persons.
An RU (Reporting Unit) consists of all members of a family unit living
together (and reporting as a single family for MEPS) or of a single
person (if living without other family members). The definition of
an RU and a MEPS family (see Section 3.3.2) are identical with the
exception of student RUs. A student RU is a young adult family member
living away from home to attend school who is linked back to his or
her family for MEPS family level analysis. Student RUs are identified
as an operational device to help obtain accurate data for the “student
living away from home” component of the general population.
An individual is in-scope at a particular point in time if (s)he is
a member of the civilian, noninstitutionalized population of the U.S.
(i.e., target population for MEPS). Since the MEPS sample is a subsample
of NHIS respondents, the chance of selection for MEPS is directly tied
to the chance of selection for the NHIS. Individuals who were in-scope
at the time of the NHIS are defined as Key persons if and only if they
were members of an NHIS household sampled for MEPS in a given year.
Persons who were not in-scope at the time of the NHIS (i.e., those
living outside the U.S., in the military, in a nursing home, or newborns)
are defined as Key if and only if they were in-scope at the time they
join an RU participating in MEPS. Therefore, in-scope persons not selected
as part of the original NHIS sample are always non-Key even if they
subsequently join a MEPS household.
Finally, a person is eligible for data collection in MEPS if (s)he
is a member of an RU containing at least one person classified as in-scope
and Key. A glossary at the end of this report (Appendix C) contains
definitions of these and other selected terms and acronyms used in
this report.
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1.3 MEPS Analytic Files
In general, three types of person-level
MEPS public use data files with appropriate weight and variance estimation
variables are released every year. These files, in sequential order
of release during the year, are referred to as: Point-in-Time (PIT),
Full Year (FY), and Longitudinal (L) data files. The FY data are released
in two phases: a preliminary “Population Characteristics File” is
released first which is superseded by a final “Consolidated File” several
months later. These two files are also known as “Use File” and “Expenditure
File” respectively, because the preliminary file is the first
to provide annual data on health care utilization while the final file
includes both utilization and associated expenditure data. Person-level
weights are included on all files while family-level weights (attached
to person-level records) are included on the PIT and FY Consolidated
files only.
As a consequence of the MEPS overlapping panel design referenced above,
data collected for the same calendar year from two consecutive MEPS
sample panels are used to develop the PIT and FY files. For example,
the 2007 PIT file comprises data from Round 1 for the Panel 12 sample
and Round 3 (2007 portion) for the Panel 11 sample. Similarly, the
2007 FY files consist of data from Rounds 1, 2, and 3 (2007 portion)
for the MEPS Panel 12 sample and from Rounds 3 (2007 portion), 4, and
5 for the Panel 11 sample. In contrast, longitudinal files contain
data for the entire two-year MEPS survey period for one specific MEPS
Panel.
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1.4 Overview of Development of MEPS Weights
Figures 3 and 4 present flowcharts
of the weight development processes for PIT and FY weights at the person-level
and family-level, respectively. These flowcharts are designed to facilitate
the descriptions of the weight development processes described in Section
2 (PIT) and Section 3 (FY) of this report. In general, the development
of MEPS weights involves a series of derivations and adjustments, with
the PIT weight for Round 1 developed first and then serving as baseline
for deriving the FY weight for a new MEPS Panel. This FY weight serves
as the starting point for developing the PIT weight associated with
the second year of data collection (i.e., Round 3 weight) for the Panel.
Adjustments for nonresponse/attrition and raking/poststratification
to control totals are incorporated at different points in the process.
Panel-specific weights for concurrent panels are ultimately combined
to produce final PIT/FY weights.
The table below lists the final weight variables provided on MEPS
public use files (PUF) that are described in the following sections
(2–6) of this report. These weights vary in derivations with
respect to reference time periods and do not apply to exactly the same
sample persons. Therefore, the pertinent sample weight should be used
to produce appropriate estimates based on MEPS data. Appendix A provides
summary distributions for 2007 of selected interim and PUF weights
mentioned in this report.
| Type of Public Use File (PUF) |
Variable Name in PUF 2 |
| Person-Level |
Family-Level |
| PIT |
WGTSP13 |
WGTRU13 |
| FY Preliminary |
PERWTyyP |
— |
| SAQ Supplement |
SAQWTyyP |
— |
| DCS Supplement |
DIABWyyP |
— |
| FY Final Consolidated |
PERWTyyF |
FAMWTyyF, FAMWTyyC |
| SAQ Supplement |
SAQWTyyF |
— |
| DCS Supplement |
DIABWyyF |
— |
| Longitudinal |
LONGWT |
— |
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Figure 3. Person-Level PIT and FY Weight Development Process
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Figure 4. Family-Level PIT and FY Weight Development Process
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2.0 Point-in-Time (PIT) Weights
The starting point for development
of the FY weights is the PIT weights. A PIT file is produced every
year to provide timely data for estimates related to health insurance
and other selected variables of interest that are available from a
single round and require minimal editing. Because two consecutive (overlapping)
panels in MEPS are fielded concurrently, data from Round 1 of the current
panel and Round 3 of the previous panel represent the same time period
and the pooling of the two rounds increases the sample sizes for estimation.
Thus, in the PIT files, Round 1 data for the most recent panel are
combined with Round 3 data from the previous panel. PIT sample weights
are constructed at both the person and family levels and can be used
to produce estimates that reflect approximately the first half of the
year and/or the date of first interview in the year. Moreover, the
PIT weight serves as the building block for constructing FY weight
variables (see Section 3.0 below).
As shown in Figures 3 and 4, the PIT weight is the result of a composite
of several factors as follows:
- a base weight (based on an interim NHIS weight),
- probability of selection for MEPS from NHIS,
- adjustments for nonresponse, and
- poststratification using external control totals.
Weights are constructed separately for the two overlapping individual
panels/rounds and then combined into a final analysis weight for the
PUF. MEPS Panel 11 spans the two calendar years 2006 and 2007 while
MEPS Panel 12 spans 2007 and 2008. The 2007 file consists of the subset
of data from the eleventh and twelfth MEPS panels covering January
1 through, roughly, the spring of calendar year 2007. More specifically,
data from the 2007 portion of the third round of data collection for
the MEPS Panel 11 sample are pooled with data from the first round
of data collection for the MEPS Panel 12 sample (see Figure 5).
Figure 5. Pooling of Overlapping MEPS Panels for PIT File
The steps used to develop the PIT person and family-level weight variables
are described in detail below.
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2.1 Development of Panel-Specific PIT Weights
2.1.1. Most Recent Panel
(Round 1)
a. Constructing Dwelling
Unit (DU) Base Weight. The MEPS DU (e.g., household) base weight is calculated
as the nonresponse adjusted NHIS household weight multiplied by the
reciprocal of the MEPS subsampling rate used to select the DU (this
rate varies by MEPS sample domain3). A constant factor is then applied
to adjust for the number of quarter/panel combinations available for
use as the MEPS sample frame from among the 16 NHIS quarter/panel combinations
(Botman et al. 2000). This factor is applied to each household weight
so that the sum of the weights can be viewed as a national estimate
of households. In most years this factor is 16/6, reflecting the inclusion
of households from 3 of 4 quarters in 2 of 4 NHIS panels.
The construction of the DU base weight can be
expressed as:
where, for DU i, WTDU 0i is the MEPS
DU base weight, WTDU Ni is the NHIS
household weight, fi is the MEPS subsampling
rate, and A0 is the constant
adjustment
factor (usually 16/6).
To reduce the impact of extremely large weights on the variances of
MEPS estimates, the extreme base weights are trimmed by reviewing the
distribution of the weights within each weight trimming class (c) defined
by the cross-classification of DU's minority status4 ,
NHIS sampling strata defined at the segment level, and the MEPS subsampling
domains.
The trimmed base weight can be expressed as
WTDU 1i = WTDU 0i x A1c with
,
where WTDU 1i is the trimmed base weight
for DU i that belongs to the trimming class c,  is
the trimming cutoff value determined for class c , and A1c is
the weight trimming factor for class c. For almost all cases A1c=
1 and only for a few cases with very large weights A1c< 1.
b. Poststratification Ratio Adjustment of Trimmed Base
Weight. To
improve the representativeness of the MEPS sample with respect to the
NHIS full sample, a poststratification ratio adjustment is applied
to the trimmed DU base weights using household level control totals,
which are estimated using the household reference person’s final
person weight in the NHIS full sample.5 The
poststratification cells are defined using the cross-classification
of MSA status, family income,
employment status of the NHIS reference person6 ,
race/ethnicity of the NHIS reference person, and reported health status
of household
members. See Appendix B.1 for detailed definitions of these variables.
The poststratified weight can be expressed as: 
where WTDU 2i is the poststratified
weight for DU i that belongs to poststratification cell c7,
A2c is
the poststratification adjustment factor, and CTDU c is
the DU level control total for cell c as derived from NHIS.
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c. Adjustment for DU Level Nonresponse in Round 1. The
poststratified DU level weight calculated above is adjusted to compensate
for nonresponding
DUs to the Round 1 interview. Using a broad range of 29 demographic,
geographic, socioeconomic and health covariates from the NHIS (see
Appendix B.2), a Chi-squared Automatic Interaction Detector (CHAID)
analysis (Kass, 1980) is carried out to form MEPS nonresponse adjustment
classes to adjust for the MEPS DU level nonresponse. Since the eligibility
status8 is known for a responding
DU only and unknown for a nonresponding DU, both eligible and ineligible
DUs are included in this adjustment.
The nonresponse adjustment is applied by inflating the weights of
the responding DUs in each adjustment cell as follows:
where WTDU 3i is
the poststratified weight for DU i which is a respondent
and belongs to the nonresponse adjustment cell c, A3c is
the nonresponse adjustment factor for cell c, r represents
the set of responding DUs, and therefore,  represents
the set of responding DUs in cell
c. That
means the adjustment factor is the ratio of the sum of the weights
of all DUs over the sum of the weights of the responding DUs in an
adjustment cell.9 As mentioned above,
the numerator and the denominator include both eligible and ineligible
DUs in this adjustment.
d. Family-Level Poststratification
Adjustment to Form Final Round 1 Family-Level Weight. After
calculation of the nonresponse adjusted DU weight above, a family-level
weight
is derived for responding
families10 by starting with the nonresponse
adjusted DU weight as the base weight and then applying a poststratification
adjustment at
the family level.11 The poststratification
is carried out using the cross-classification of the following variables:
family type, race/ethnicity
of reference person12, region, MSA
status, age category of reference person, and
number of eligible family members (see Appendix B.3).
The March Current
Population Survey
(CPS)
family-level totals are
used as control totals for this adjustment.
This adjustment also
serves as an adjustment for nonresponse at the family level to yield
the final Round 1 family weight.
More specifically, the final family weight (WTFM1) for
Round 1 can be expressed as:
where WTFM0j is the base family
weight and WTFM1j is the Round 1 final
weight for family j ; Fc is the poststratification
adjustment factor for cell c , indicates the
set of responding families within cell c, and CTFMc is
the family-level control total for cell c. The distribution of this
weight
is reviewed, and very large weights, if any, are trimmed to the level
of highest acceptable weight, and the poststratification adjustment
is repeated.
Only families that meet the following conditions are assigned an
initial weight and included in poststratification adjustment to produce
the final Round 1 family weight:
- at least one Key in-scope person in the family during Round
1,
- the reference person in the family is Key, and
- all Key in-scope family members have a positive person weight.
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e. Person-Level Poststratification Adjustment to Form
Final Round 1 Person-Level Weight. For reference
persons and married persons with spouse present under the age
of 65 (i.e.,
subgroup g1), the final family weight produced in
step d above is assigned as their final person weight.13 For
the remaining persons (i.e., subgroup g2 ), poststratification
at the person level of the family weight produced in step d above,
is carried out using the March CPS control totals to yield the
final Round 1 person weight.14 The
variables used in the poststratification are: region, race/ethnicity,
sex, and age category (see Appendix
B.4).
The derivation of the final Round 1 person k weight
for person (WTPR1k) can be expressed as follows:
where, WTPR0k is the base weight of
person
k who belongs to family j15,
P1c is the adjustment factor for cell
c. For group g1, since no poststratification
adjustment is applied, P1c =1. For group
g2, the numerator of the adjustment factor is obtained
by subtracting the weighted total for group g1 from
the overall control total CTPRc for both groups
in cell c i.e., an estimated control total for group g1
in cell c, and the denominator of
the adjustment
factor is the sum of weights of persons in group g2 in
cell c. Similar to the family weight, outlier weights are trimmed
and the poststratification
process is repeated if any trimming is done.
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2.1.2 Preceding Panel (Round 3)
a. Initial Person Weight for Round
3. The
initial person-level weight assigned to Round 3 respondents is the
Full Year
(FY) person weight
from the previous year  (see
Section 3.1.1 below for general description of how this weight is
derived); an asterisk is used to denote that the weight is for the
prior year of the preceding panel (now in its second year). Persons
in the FY file who were not in-scope during the Round 3 portion of
the second year are not included in PIT estimation.
b. Poststratification Adjustment
to Compute Final Round 3 Person-Level Weight. A
poststratification adjustment of the initially assigned person
weight from step c above is carried
out using the current
year March CPS control totals for the U.S. civilian noninstitutionalized
population to yield the final Round 3 person weight. The variables
used in forming poststratification cells are sex, age category, race/ethnicity,
and Census region (see Appendix B.5). The poststratified weight for
person k can be expressed as:
where  is
the poststratified Round 3 final weight for person k who
belongs to poststratification cell c,  is
the FY weight for person k from the previous year as discussed
above, P3c is the poststratification adjustment factor,
and CTPRc is the March CPS control total
for cell c. As usual after any poststratification adjustment,
outlier weights are
trimmed and the poststratification adjustment is repeated if any
trimming is done.
c. Poststratification Adjustment to Form Final Round 3 Family-Level
Weight. First, a family-level initial weight is assigned using the
person-level weight (from step 2.1.2b above) of the reference person
of the family. Then a poststratification adjustment at the family
level is carried out using the March CPS family-level control totals
to yield the final Round 3 family weight. The variables used in the
poststratification are family type, race/ethnicity of the reference
person, region, MSA status, age category of the reference person,
and number of eligible members in the family (see Appendix B.3).
The family-level weight for Round 3 can be expressed as follows:
where  is
the initial weight for family and j and
 is the weight of
person k from the previous step, where person k is
the reference person of family j. Then the poststratified
family weight for Round 3 can be expressed as:
where  is the poststratification
adjustment factor for cell c and
CTFMc is the family-level control total for cell c. After the adjustment,
extremely large weights are trimmed and the poststratification process
is repeated if any trimming is done.
Similar to Round 1, only families that meet the following conditions
are assigned an initial weight and included in poststratification
adjustment to produce the final Round 3 family weight:
- at least one Key in-scope person in the family during
the second year portion of Round 3,
- the reference person in the family is Key, and
- all Key in-scope family members have a positive person weight.
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2.2 Development of Combined-Panel PIT Weights
2.2.1 Person-Level
a. Assigning Compositing
Factors to Panel-Specific Weights in the Combined Panel. The panel-specific
files are put together to create a combined person-level file of
both panels. A compositing factor is applied to the weights of each
individual panel to derive the weight for the combined panel. The
compositing factor is calculated so that it reflects the number of
respondents in each individual panel relative to the total number
of respondents in both panels combined. The PIT composite weight
for person in the combined panel can be expressed as follows:
where WTPR1k is
the final Round 1 person weight from the recent panel,  is the Round 3 final person weight
from the preceding panel, and  is the compositing factor which is the proportion of
total persons in the combined panels who came from the recent panel.
In recent
years, the values of generally
ranged from around 0.45 to 0.55.
b. Poststratification
Adjustment to Produce Final Person-Level PIT Weight. A
poststratification adjustment is applied to the composite person
weight in the combined panel by
using the March CPS control totals. The variables used for this poststratification
are sex, race/ethnicity, age category, region, and MSA status (see
Appendix B.5). The poststratified final PIT person weight (PERWTPITk ) for
person k can be expressed as:
where PPITc is
the poststratification adjustment factor and CTPRc is
the person-level control total based on the March CPS for poststratification
cell c that includes person k. After the adjustment,
outlier weights are trimmed and the poststratification process is
repeated if any trimming is done. This poststratified weight is named
WGTSP13 in the PUF.
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2.2.2 Family-Level
a. Assigning Compositing
Factors to Panel-Specific Weights in the Combined Panel. Similar
to the person level, the panel-specific family-level datasets are
put together
to create a family-level dataset of responding families of both panels
combined. The same compositing factor used for the person-level is
applied to the weights of each individual panel to derive the family-level
weight for the combined panel. The PIT composite weight for family
j in the combined panel can be expressed as:
where WTFM1j is
the Round 1 family weight from the recent panel,  is
the Round 3 family weight from the preceding panel and is
the compositing factor as derived for the person-level compositing.
b. Poststratification
Adjustment to Produce Final Family-Level PIT Weight. A
poststratification adjustment is applied to the family weight in
the combined panel to the same
March CPS family-level control totals used for the individual panel-specific
family weights. Similar to the person-level poststratification adjustment
described above, the cells available for the combined sample are
more comprehensive and refined due to the increased sample size.
The variables used for the poststratification are family type, race/ethnicity
of the reference person, region, MSA status, age category of the
reference person, and number of eligible members in the family (see
Appendix B.3). The poststratified final PIT family weight (FAMWTPITj )
for family j can be expressed as:
where FPITc is
the poststratification adjustment factor and CTFMc is
the family-level control total based on March CPS for cell c
that includes family j. Also, at this stage, extremely
large weights are trimmed and the poststratification process is repeated
if any trimming is done.
This family-level weight is assigned to all members of the family
who are eligible to receive a family weight and is named WGTRU13
in the PUF.
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2.3 General Issues Related to Developing PIT Weights
a. Cell Collapsing. The initial nonresponse
or poststratification cells created in different steps are collapsed in some
instances to avoid very small cell sizes or large adjustment factors. Generally,
a cell size of at least 20 in the MEPS file and a cell size of at least 100
in the control total file (e.g., CPS) are considered acceptable for nonresponse
or poststratification adjustments. In addition, cells with adjustment factors
greater than two times the average adjustment factor are usually either truncated
or collapsed with a neighboring cell.
b. Weight Trimming. The distribution of weights is examined after each round
of poststratification adjustments to determine whether there are any inordinately
large values. Then weights with inordinately large values are trimmed in a
manner designed to reduce overall MSE (i.e., slight increases in bias more
than offset by reductions in variance). If any trimming is done then the poststratification/raking
procedure is repeated.
c. Zero Weighted Cases. Most persons in MEPS public use files have a positive
value for both the person and family weight variables. However, a small proportion
of cases are assigned a value of zero for either the person or family weight.
The conditions when sample persons are assigned a value of 0 for the person
or family-level weight are described below:
Person Weight. A person
is assigned a person weight of zero (but a positive family weight) if the following
two conditions are met: (1) the person is
either non-Key or in the military for the entire period but living at home;
and (2)
the person is a member of a family that has been assigned a positive family-level
weight.
Family Weight. A person
is assigned a family weight of 0 (but a positive person weight) when either:
(1) the person
is a member of a family in which
at least
one Key in-scope member does not have a positive person weight (due to
nonresponse); or (2) the reference person of the family is non-Key16 .
Appendix A provides summary distributions for 2007 of selected interim and
PUF weights discussed in this report.
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3.0 Full Year (FY) Weights
MEPS full year data are released in two
phases: a preliminary full year “Population Characteristics File” (a.k.a.
Use File) is released first which is superseded a few months later by a final
full year “Consolidated File” (a.k.a. Expenditure File). The preliminary
file contains all annual survey data except medical expenditure and income/tax-related
variables which require a longer time to process and thus are included in the
final consolidated file. Moreover, the weights are not identical in the two
full year files because income data that are not available at the initial release
are used to refine the weight variables for the final release. More specifically,
an adjustment using poverty status is incorporated into the final Consolidated
File weight. The FY files allow analysts to produce person-level estimates
for the U.S. civilian noninstitutionalized population (i.e., the in-scope or
target population) at any time during the year and/or slightly more restricted
cross-sectional estimates for the U.S. civilian noninstitutionalized population
on December 31. In addition, weights are included in the FY Consolidated File
that can be used to produce family-level estimates based on two slightly different
definitions of family units (CPS versus MEPS).
Full year weights are the result of a composite of several factors as follows:
- the previously constructed PIT weight (see Section 2 above),
- adjustments for person level nonresponse (survey attrition), and
- raking/poststratification adjustments.
Weights are constructed separately for the two overlapping individual panels/rounds
and then combined into a final weight for the PUF. The steps used to develop
the FY person and family-level weight variables are illustrated in Figures
3 and 4 respectively and described in details below.
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3.1 Development of Panel-Specific FY Weights
3.1.1 Most Recent Panel (Rounds
1–3)
a. Initial Weight. The
final Round 1 person-level weight used to develop the PIT weight (see Section
2.1.1 above) is assigned
as the initial weight for the FY person weight. Therefore, the initial FY weight
for person k is WTPR1k where WTPR1k is
the final Round 1 weight for person k.
b. Adjustment for Person-Level Nonresponse. The initial weight is adjusted to compensate for person-level nonresponse over
Rounds 2 and 3 (referred to as year 1 nonresponse). Only those individuals
who are Key and were ever in-scope during the year are included in developing
the adjustment factor. The respondents are those individuals who responded
for their entire period of eligibility over Round 2 and the year 1 portion
of Round 3, and the nonrespondents are those who did not respond for some part
of their eligibility over Round 2 and the year 1 portion of Round 3. To form
nonresponse adjustment cells, a CHAID17 analysis is carried out using a set
of potential predictor variables. The set of 11 predictor variables used as
input
to the CHAID analysis to adjust for this year 1 attrition is detailed in Appendix
B.7.
The nonresponse adjustment is applied to
the weights of the responding persons in each adjustment cell c as follows.
where WTPR2k is the
nonresponse adjusted weight for person k who belongs to nonresponse
adjustment cell c, P2c is the nonresponse adjustment factor
for cell c, r represents the set of responding persons, and therefore,
represents the set of responding persons in cell c.
The adjustment factor is the ratio of the sum of weights of all persons over
the
sum of the
weights of the responding persons in cell c.
c. Person-Level Raking/Poststratification
Adjustments. This step depends on the in-scope status of a person on December
31 as follows:
- Raking Adjustment for Persons In-Scope
on December 31. The nonresponse adjusted weights of all Key
in-scope responding persons on December 31 (about 99 percent of cases)
are raked to December 31
control totals estimated based on the subsequent March CPS estimates of
the U.S. civilian noninstitutionalized population and Census Bureau’s
population estimates for January 1. The raking dimensions used in the
adjustment are based
on various combinations of the following variables: race/ethnicity, sex,
census region, MSA status, and age category (see Appendix B.6).
- Poststratification Adjustments for Persons Not In-scope on December 31.18
The small proportion of cases who are not in-scope at the end of the year
(total of only about 1 percent) are adjusted as follows:
Decedents. A special poststratification is applied to
the weights of respondents who died during the target year using control
totals derived from vital statistics
data that have been adjusted to eliminate estimated deaths among nursing
home residents.19 Separate decedent control
totals are used for persons under age 65 and persons age 65 and over.
Nursing Home Entrants. A second special poststratification
adjustment is applied to the weights of those who entered a nursing home
prior to December
31 and who were not members of the U.S. civilian noninstitutionalized population
on December 31 using an estimated control total.20
Other Not In-scope Persons on December 31. For out-of-scope persons on December
31 who do not belong to the two special out-of-scope groups defined above
(decedents and nursing home entrants), the FY weight is set equal to their
nonresponse adjusted weight without any further adjustment.
The FY weight for person k in year 1 in the recent panel can be expressed
as:
where,
PFY1k=raking
adjustment factor21 for
person k who was in-scope on December 31
= poststratification adjustment factors for the two special out-of-scope
groups i.e., decedents and nursing home entrants
= 1 for other out-of-scope persons on December 31.
The distribution of the raked/poststratified weights is examined
to identify and trim extremely large values and the raking/poststratification
process is repeated if any trimming is done.
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3.1.2 Preceding
Panel (Rounds 3–5)
a. Initial Weight. The year
1 full year person weight derived for this panel in the previous year after
Rounds 1–3
is assigned as the initial weight for the second year for the panel. See
Section 3.1.1 above for the derivation
of year 1 FY weight for the recent panel. Therefore, the initial weight for
person k at this step can be denoted by  ,
an asterisk used to indicate the same weight for the preceding panel.
b. Adjustment for Person-Level Nonresponse. The
initial weight from above is adjusted to compensate for year 2 nonresponse
over Rounds 4 and 5. A CHAID
analysis is again used to form nonresponse adjustment cells based on a set
of potential predictor variables (see Appendix B.8 for list of variables).
Since the nonresponse adjustment procedure is the same as described above
for the other panel, without repeating the detailed steps here the nonresponse
adjusted weight for person k in this panel will be denoted as .
c. Person-Level Raking/Poststratification Adjustments. As for the other
panel, this step depends on the in-scope status of a person on December 31
as follows:
- Raking Adjustment for Persons In-Scope on December 31. The
nonresponse adjusted weights of all Key in-scope responding persons on
December 31 (about 99 percent
of cases) are raked to December 31 control totals estimated based on
the subsequent March CPS estimates of the U.S. civilian noninstitutionalized
population and Census Bureau’s population estimates for January
1. The raking dimensions used in the adjustment are based on various
combinations
of the following variables: race/ethnicity, sex, census region, MSA status,
and age category (see Appendix B.6)22 .
- Poststratification Adjustments for Persons Not In-scope on December
3123 . As for the other
panel, special poststratification adjustments are applied to the weights
of decedents and nursing home entrants and no adjustment
is applied to the weights of the remaining persons who were not in-scope
on December 31 (see section 3.1.1c (ii) above).
Therefore, the FY weight for person k in year 2 of the preceding panel can
be expressed as:
where,
 =
raking adjustment factor for person k who was in-scope on December
31
= poststratification adjustment factors for the two special out-of-scope
groups i.e., decedents and nursing home entrants
= 1 for other out-of-scope persons on December 31.
As for the most recent panel, the distribution of the raked/poststratified
weights is examined to identify and trim extremely large
values and the raking/poststratification process is repeated if any
trimming is done.
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3.2
Development of Combined-Panel Person Weights24 for
FY Population Characteristics
(Use) File
a. Assigning Compositing Factors
to Panel-Specific Weights in the Combined Panel. The panel-specific
FY files are put together to create a combined person-level FY file and
a compositing factor is applied
to the panel-specific FY weight of each individual panel to derive the FY
weight for the combined panel (a.k.a. use file weight). The compositing factor
is calculated so that it reflects the number of respondents for each individual
panel relative to the total number of respondents in both panels combined.
The FY composite weight for person k in the combined panel can be expressed
as:
where WTPRFY1k is
the FY weight for year 1 for the recent panel,  is
the FY weight for year 2 for the preceding panel, and
 is the compositing factor—which is the proportion of total persons
in the combined panels who came from the most recent panel. In recent years,
the values of generally ranged from around 0.45 to 0.55.
b. Raking Adjustment of the
FY Composite Weight. The resulting composite person weights
(excluding decedents and nursing home entrants) are raked to the same
December CPS based control totals used
for the individual panel FY weights. The raking dimensions used in this adjustment
are based on various combinations of the following variables: race/ethnicity,
sex, Census region, MSA status, and age category (see Appendix B.6).25 The
decedents and nursing home entrants are separately poststratified as described
in Section 3.1.1.c above. These adjustments produce the PUF variable PERWTyyP
i.e., preliminary FY weight.
Since this step is the same as in Section 3.1.1.c, without going into the
details, the preliminary FY weight for person k in the combined panel can
be expressed as:
where PPFYk is the raking/poststratification adjustment factor. The distribution
of the adjusted weight is checked for outlier weights and the raking procedure
is repeated if any weight trimming is required. This weight is called preliminary
FY (PFY) weight because the poverty status is not included in the raking
adjustment yet.
Note that no family weight is produced for the FY Population Characteristics
File.
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3.3 Development of Final FY Weights for Consolidated File
3.3.1 Person-Level
To produce the final person-level FY consolidated
file weight (a.k.a. expenditure file weight), the person-level weights produced
for the Population Characteristics File are re-raked using poverty status26 in addition to the same set of variables used before (see above and Appendix
B.6) corresponding to the estimated control totals for December 31. Persons
who are out of scope on December 31 are excluded from this raking so preliminary
FY weights for these persons are carried forward from the previous step without
any further adjustment. This produces the PUF variable PERWTyyF. Therefore,
the final FY weight for person can be expressed as:
with PFYk represents
the complete iterative raking adjustment factor for person k. The
distribution of the final weight is checked, and outlier weights, if any,
are trimmed
followed by reapplication of the raking procedure.
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3.3.2 Family-Level
Two final family-level weights are derived for the FY consolidated file;
one based on the CPS definition of a family (PUF variable FAMWTyyC) and the
other based on the MEPS definition of a family (PUF variable FAMWTyyF). In
addition to the difference in family definitions, there is also a difference
in temporal scopes of these two weights. The CPS family weight is derived
to produce estimates only for those families in-scope on December 31 of the
year while the MEPS family weight is derived to produce estimates for all
in-scope MEPS families that existed any time during the year. In other words,
the MEPS family weight applies to families in-scope on December 31 plus the
families whose members became out-of-scope prior to the end of the year.27
While the CPS and MEPS definitions of family units are identical in most
instances, unmarried partners who identify themselves as a single family
unit are considered to be a single family in MEPS but represent two separate
families in the CPS. In addition, foster children are considered to be family
members in MEPS but not in the CPS. The control totals for a family-level
raking adjustment are obtained from the CPS and represent families in existence
on December 31 of a given year. CPS-like families are formed from the MEPS
families in existence on December 31. For those MEPS families that are split
to form multiple CPS-like families, each CPS-like family is assigned a reference
person. The initial CPS family weight assigned is the person weight of the
reference person of the CPS-like family. Then, raking adjustments are applied
to this initial family weight to obtain the final CPS family weight. For
those MEPS families in-scope on December 31, the raked CPS family weight
of the MEPS reference person is assigned as the final MEPS family weight.
For persons in the small number of MEPS families that are out-of-scope at
the end of the year, the person-level weight of their reference persons serves
as their final MEPS family weight.
Only families that meet the following conditions are assigned an initial
weight and included in poststratification adjustment to produce final FY
family weights:
- at least one Key in-scope person in the family during the year,
- the reference person in the family is Key, and
- all Key in-scope family members have a positive person weight.
The following steps are used to derive the CPS and MEPS family weights:
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a. Initial CPS Family Weight. After forming the
CPS families, a family-level initial weight is assigned to all responding
CPS families using the person-level
weight of the reference person of the CPS family. Therefore, the initial
family-level weight for the CPS family js can be defined as:
where PERWTFYk is the weight of person k who
is the reference person of CPS family js. 28
b. Raking Adjustment to Produce CPS Family Weight. A family-level raking
adjustment, using various combinations of family type, race/ethnicity of
the reference person, poverty status, region, MSA status, family size, and
age category of the reference person as raking dimensions (see Appendix B.9),
is then applied to the initial CPS family weight. The raking adjustment is
applied only to the eligible CPS families (i.e., those with a Key reference
person) that are in-scope on December 31 of the year. The control totals
at the family level for December 31 are derived by calibrating the estimates
obtained from the March CPS of the following year to December 31 using an
estimated monthly average growth rate for the total population of families.
The raked family-level FY weight for the CPS family js can
be expressed as:
where FFYjs is the raking adjustment factor for CPS
family js. The raking procedure is repeated if any trimming
of large weights is necessary.
This family-level FY weight is assigned to all persons within a CPS family
who are eligible to receive a family weight29 . All persons in families not
in-scope on December 31 or persons in families with a non-Key reference
person are assigned a zero CPS family weight30 . This produces the PUF variable
FAMWTyyC.
c. Producing MEPS Family Weight. Finally, the MEPS family weight at the
person-level is assigned based on the MEPS definition of families. This is
done by assigning the CPS family weight of the reference person of the MEPS
family (as derived above) to all members of the MEPS family, which becomes
FAMWTyyF. If the MEPS family is not in-scope on December 31 then the person-level
weight (as derived in section 3.3.1) of the reference person of the MEPS
family is assigned to all members of the MEPS family.
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3.4 General Issues Related to Developing FY Weights
The general issues discussed in relation
to the development of PIT weights in Section 2.3 also apply to the development
of FY weights. In other words, the same principles are used for cell collapsing,
weight trimming after each raking/poststratification adjustment, and assigning
zero weights to persons and families. However, raking procedures are not used
in the PIT weighting procedures but are used in the development of FY weights.
Generally, a cell size of at least 100 in the MEPS file and a cell size of
at least 500 in the control total file (e.g., CPS) for a category within a
raking dimension are considered acceptable in the MEPS raking procedures.
Appendix A provides summary distributions for 2007 of selected interim and
PUF weights discussed in this report.
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4.0 Weights for Survey Supplements
In addition to the person and family-level
weight variables included on FY files, two additional person-level weight variables
are included for appropriate estimation using data collected in the MEPS Self-Administered
Questionnaire (SAQ) or Diabetes Care Supplement (DCS). These supplements are
self-administered paper and pencil questionnaires that are fielded in selected
rounds of the survey to all adults and to adults identified as having diabetes,
respectively. In general, the weight variables for these supplements are used
in lieu of the FY person-level weight when the analysis involves data from
the supplement.31 As for the general survey FY weights described in Section 3.0
above, preliminary weights for supplements are provided on the preliminary
FY file while final weights for supplements are provided on the final FY file.
The following are overviews of procedures for developing these special supplement
weight variables.
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4.1 Self-Administered Questionnaire (SAQ)
An SAQ questionnaire is requested to be
completed by each adult (persons aged 18 and older) family member in Round
2 (Panel X) and Round 4 (Panel X-1) to obtain additional information for
measures of adult health status and health care quality32 . Thus, the target
population for the SAQ is the adult civilian, noninstitutionalized population
at the time data were collected for Rounds 2/4. Following is a summary of
the procedure for developing weights to be used when producing estimates
of data collected in the SAQ:
a. The SAQ weight is developed starting with initial weights used for developing
the panel-specific FY weight for each panel (see Sections 3.1.1.a and 3.1.2.a).
Based on these panel-specific initial weights, a composite weight is developed
by applying the same factors used for combining the panel-specific FY weights
(see Section 3.2.a). This composite weight is then adjusted for both nonresponse
over the year33 and to the SAQ. Variables used in the nonresponse adjustment
process are region, MSA status, family size, marital status, level of education,
health status, health insurance status, age category, sex, and race/ethnicity
(see Appendix B.10).
b. The nonresponse adjusted SAQ weight in step 1 above is raked to the CPS
estimates corresponding to December of the analytic year (the same source
of control figures used for the full year person weights) to produce the
preliminary SAQ weight (SAQWTyyP) for the FY Population Characteristics File.
The variables used in the raking adjustment of preliminary SAQ weights are
region, MSA status, age category, sex, and race/ethnicity, as were used for
the preliminary FY person weights. The only difference is that age categories
are developed after excluding ages under 18, since only adults were eligible
for the SAQ.
c. For the final FY SAQ weight, the
weight in step b above is raked again to CPS estimates based on the five
variables mentioned in step b as well as poverty status to produce the
final SAQ weight (SAQWTyyF) for the final FY consolidated data file.
As usual, for both preliminary and final
SAQ weighting, after raking the distribution of the weights is checked for
outliers and the raking procedure is repeated if any weight trimming is implemented.
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4.2 Diabetes Care Supplement (DCS)
The DCS is fielded during Round 3 (Panel
X) and Round 5 (Panel X-1) to collect a variety of measures from adults
reported to have been told by a health professional that they had diabetes.
All adults who reported on the CAPI questionnaire to have been diagnosed
with diabetes are administered the DCS questionnaire. Following are the
steps used to construct the DCS weight for use when producing estimates
for data collected in the DCS:
a. To produce the DCS weight for the
preliminary FY file, the initial weight assigned is the SAQ preliminary
weight derived for the FY preliminary
file (SAQWTyyP—see Section 4.1 above).
b. The DCS initial weight from (a) above is then adjusted for nonresponse
to the main CAPI diabetes question. The variables used in CHAID analysis
as potential predictors of response propensity to form the nonresponse
adjustment classes include region, MSA status, family size, marital status,
level of education, health status, health insurance status, age category,
sex, race/ethnicity. This is the same set of variables used for SAQ nonresponse
adjustment as presented in Appendix B.10.
c. Finally, the weight from (b) above is adjusted for nonresponse to
the DCS questionnaire (generally about 10%) to produce the DCS weight
for the
preliminary FY file (DIABWyyP). The nonresponse adjustment classes
for this stage are formed using race/ethnicity, sex, and age category.
Note
that the age categories (age at the date of the interview) used differ
from those in stage (i) above. These are: 18–29; 30–44; 45–64;
65+.
d. To produce the final DCS weight for the FY consolidated file (DIABWyyF),
steps a to c above are repeated but substituting the final SAQ weight (SAQWTyyF)
as the initial weight in step a.
For both preliminary and final DCS weighting, the nonresponse adjusted
weights are checked for outliers and a weight trimming procedure is applied
as necessary, followed by an adjustment of the sum of weights.
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5.0
Longitudinal (L) Weights
In contrast to the PIT and FY files
which include persons from two consecutive overlapping panels, the persons
included in a longitudinal data file are from one specific sample panel
and represent those who were in the MEPS population (U.S. civilian noninstitutionalized)
for all or part of a given two-year period (e.g., Panel 11: 2006–2007).
Although data are available for all five rounds for more than 90% of the
cases in most longitudinal files, persons who were born, died, were in
the military or an institution, or left the country during the two-year
period do not have data for one or more rounds. In contrast, persons in
the panel who participated in the survey for only part of the period they
were in-scope are treated as nonrespondents and not included in this file.
The longitudinal weight variable (described below) reflects adjustments
for this attrition (nonresponse).
To derive the longitudinal person-level weight, a panel is divided into three non-overlapping groups as follows:
a. All persons in their year 2 FY file who are in-scope on December 31st of year 2 or who are out-of-scope (OOS) due to death or entering a nursing home on December 31st of year 2.
b. All persons in their year 2 FY file who are OOS on December 31st of year 2 for reasons other than death or entering a nursing home.
c. All persons in their year 1 FY file from the panel who are OOS on December 31st of year 1 and not part of the year 2 FY file.
The longitudinal weight for person k is then assigned as follows:
where a, b,& c are three groups as defined above, PERWTFY2k is the panel-specific final
poverty adjusted year 2 annual weight for person
k, and PERWTFY2k is the panel-specific final poverty adjusted year 1 annual weight for person k. Both these weights34
have been
adjusted to compensate for survey attrition during the year. Lk is an adjustment factor
designed to make the sum of the longitudinal weights
of the persons in group b
equal to the sum of the combined panel FY person weights of similar OOS persons from both panels in the year 2 FY file.35
The adjustment factor Lk for person k can be expressed as:
where  is the sum of combined panel FY weights of persons in both
panels who are OOS on December 31st for reasons other than death or entering a nursing home and
is the sum of panel-specific year 2 FY weights of persons in group b of the longitudinal panel only. In other words, the numerator includes all OOS persons as specified above from both panels in the FY file and the denominator includes the same OOS persons from the longitudinal panel only.
Beginning with panel 14, the adjustment factor Lk will no longer be applied to group b (i.e., Lk = 1 will be used in the above expression for deriving the longitudinal panel weight).
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6.0 Variance Estimation
The MEPS-HC data is collected using a complex
multistage sample design that involves stratification, clustering, and unequal
selection probabilities. Unlike the data obtained through a simple random sample
design where all observations are independent with equal sampling weights,
the MEPS data are correlated due to clustering and have unequal weights. Moreover,
the MEPS weighting procedures employ differential adjustments for nonresponse,
coverage, and poststratification/raking. These sample design and estimation
complexities require special consideration in computing variances/standard
errors of MEPS estimates. Therefore, a variance estimation method under the
assumption of a simple random sample as employed by the most commonly used
statistical packages is not appropriate for MEPS. These software packages will
usually underestimate the variance of MEPS estimates. To obtain accurate estimates
of the variances of MEPS person- or family-level estimates for either descriptive
statistics or more sophisticated analyses based on multivariate models, the
MEPS sample design complexities must be taken into account using special analysis
approaches developed for complex surveys. A review of commonly used approaches
to design-based estimation of the variances of estimates from complex survey
data can be found in Wolter (2007) and Shao (1996). The two most commonly used
variance estimation methods for complex survey data are the Taylor series linearization
method and Balanced Repeated Replication (BRR) method. Various software packages
that use these approaches to analyze data from complex surveys are SUDAAN,
STATA, WESVAR, and SAS Proc Survey procedures.
The Taylor series variance estimation method is most
commonly applied when analyzing MEPS data. MEPS annual public use files include
the two necessary
sample design variables for implementing this method. These variables identify
the variance estimation strata (VARSTR) and variance estimation clusters (VARPSU).
Specifying these variables in conjunction with a ‘with replacement’ design
in software packages that employ the Taylor series approach (e.g., SUDAAN,
STATA, or SAS Proc Survey procedures) will produce variances that reflect the
complexities
of the MEPS design.
Because it can be extremely difficult to use Taylor series to calculate the
variances of complex estimators not readily available in complex survey software
packages (e.g., two-part model of health expenditures, ratio between two medians),
a linkage file containing a BRR replication structure (in the form of a set
of half sample indicators) is also available for variance estimation (http://www.meps.ahrq.gov/mepsweb/data_stats/download_data_files_detail.jsp?cboPufNumber=HC-036BRR
(accessed September 16, 2010). The file is called ‘Replicates for Calculating
Variances File’ and includes all cases from 1996 to the current year.
The half sample indicators in this file (+1 and -1) can be used to form BRR
replicate weights to compute variances of MEPS estimates using either BRR or
Fay’s BRR (Fay 1989) methods.
To facilitate analysis of subpopulations and/or low prevalence
events, it may be desirable to pool together more than one year of MEPS-HC
data to yield
sample sizes large enough to generate reliable estimates. MEPS-HC samples from
year to year are not completely independent because households are drawn from
the same sample geographic areas and many persons are sample respondents for
two consecutive years (see MEPS-HC Methodology Reports for more details at http://www.meps.ahrq.gov). Despite this lack of independence, it is valid to
pool multiple years of MEPS-HC data and keep all observations in the analysis
because each year of MEPS-HC is designed to be nationally representative. However,
to obtain appropriate standard errors when pooling years of MEPS-HC data, it
is necessary to insure a variance structure that consistently specifies MEPS
geographic sampling units across years.
Starting in 2002, the annual MEPS public use files were released with a common
variance structure that allows users to seamlessly pool annual files from 2002
onward. Prior to 2002, however, each annual MEPS public use file was released
with a variance structure unique to the particular MEPS sample in that year.
Therefore, when one or more years of data being pooled precede 2002, it is
necessary to obtain a common variance structure from the Pooled Estimation
Linkage File (http://www.meps.ahrq.gov/mepsweb/data_stats/download_data_files_detail.jsp?cboPufNumber=HC-036)
when producing pooled estimates using the Taylor series method. This file provides
a common variance structure (i.e., consistent specification of MEPS geographic
sampling units) across all years since the inception of MEPS in 1996. In addition,
the Replicates for Calculating Variances File provides standardized replicates
across all panels to facilitate appropriate BRR variance estimation from pooled
data. However, pooling 1999 or 2000 with other years using the BRR file is
inadvisable due to inconsistencies resulting from some primary sampling units
(PSUs) that were dropped in those years.
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7.0 References
Botman S.L., Moore T.F., Moriarity C.L.,
Parsons V.L. Design and Estimation for the National Health Interview Survey,
1995–2004. National Center for Health Statistics. Vital Health Stat 2(130).
2000.
Ezzati-Rice, T.M., Rohde, F., Greenblatt,
J., (2008). Sample Design of the Medical Expenditure Panel Survey Household
Component, 1998–2007.
Methodology Report No. 22. March 2008. Agency for Healthcare Research and Quality,
Rockville,
MD. http://www.meps.ahrq.gov/mepsweb/data_files/publications/mr22/mr22.pdf
Kass. G. V. (1980). “An Exploratory Technique for Investigating Large
Quantities of Categorical Data.” Journal of Applied Statistics, Vol.
29, No. 2 (1980), pp. 119–127.
Korn E. and Graubard B. (1999). Analysis of Health Surveys. John Wiley and
Sons Inc. New York.
Shao, J. (1996). “Resampling Methods in Sample Surveys (with discussion).” Statistics,
27, 203–254.
Wolter, K.M. (2007). Introduction to Variance Estimation. 2nd Edition.
New York: Springer-Verlag.
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Appendix A. Distribution of Weights at Different Stages of Weighting for 2007 MEPS
| Panel/Year |
Weight |
PUF Variable |
Number of Records |
Sum of Weights |
Minimum Weight |
Median Weight |
Average Weight |
Maximum Weight |
CV Weights (%) |
| Panel 12, 2007 |
DU Final Weight |
- |
5,525 |
116,942,394 |
4,406 |
20,345 |
21,166 |
116,377 |
48.6 |
| Round 1 Family Weight |
- |
5,736 |
129,215,974 |
4,266 |
20,491 |
22,527 |
104,048 |
54.0 |
| Round 1 Person Weight |
- |
14,819 |
296,056,836 |
3,152 |
17,823 |
19,978 |
106,987 |
58.9 |
| Panel 11, 2007 |
Round 3 Person Weight |
- |
17,008 |
296,056,836 |
679 |
15,183 |
17,407 |
118,825 |
69.1 |
| Round 3 Family Weight |
- |
6,680 |
129,215,974 |
1,036 |
17,208 |
19,344 |
109,389 |
66.2 |
| Panels 11 & 12 Combined, 2007 |
PIT Person Weight |
WGTSP13 |
31,827 |
296,056,836 |
329 |
8,170 |
9,302 |
63,811 |
65.3 |
| PIT Family Weight |
WGTRU13 |
12,416 |
129,215,974 |
417 |
9,296 |
10,407 |
57,102 |
62.2 |
| Panel 12, 2007 |
FY Person Weight* |
- |
13,015 |
301,170,737 |
2,338 |
20,447 |
23,140 |
131,419 |
60.5 |
| Panel 11, 2007 |
FY Person Weight* |
- |
16,355 |
300,972,329 |
1,154 |
16,032 |
18,402 |
120,178 |
68.8 |
| Panels 11 & 12 Combined, 2007 |
FY Person Weight (Preliminary) |
PERWT07P |
29,370 |
301,309,149 |
651 |
8,994 |
10,259 |
67,646 |
65.4 |
| FY Person Weight (Final) |
PERWT07F |
29,370 |
301,309,149 |
550 |
8,902 |
10,259 |
67,154 |
67.7 |
| FY Family Weight (CPS) |
FAMWT07C |
11,873 |
130,346,831 |
540 |
9,644 |
10,978 |
61,163 |
65.1 |
| FY Family Weight (MEPS) |
FAMWT07F |
11,615 |
127,885,890 |
540 |
9,682 |
11,010 |
61,163 |
64.9 |
| Panel 11, 2006-07 |
Longitudinal Weight |
LONGWT |
16,533 |
304,831,607 |
958 |
15,908 |
18,438 |
120,341 |
71.0 |
| *The weight distributions for these
weights do not reflect the special weight adjustments applied to persons
not in-scope on December 31 (i.e., for decedents and nursing home entrants). |
Return
to Table of Contents
Appendix B. Variables Used in Nonresponse and Poststratification/Raking Adjustments38
B.1 Variables Used in DU-level Poststratification
Using NHIS Control Totals
- MSA status:
In MSA in the principal city
In MSA but not in the principal city
Not in MSA
- Race/ethnicity of the DU reference person:
Hispanic
Black, non-Hispanic
Asian
Other
- Income category of the DU:
Income<$20,000
Income between $20,000 to 34,999
Income>$34,999
Income>$20,000 but exact value is unknown
Income Unknown
- Reported health condition:
All members of the DU with good to excellent health
Other
- Employment status of the DU reference person:
Employed
Not employed
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of Contents
B.2 NHIS Variables Used in CHAID Analysis to Form Cells for DU-level NR Adjustment
(* indicates significant variables in 2007)
- Any Asian in household (indicator for MEPS oversampling):
no Asian in the household
at least one person is Asian in the household
- Predicted poverty for household (indicator for MEPS oversampling):
no RU in the DU with predicted poverty > 0.3
at least one RU in the DU with predicted poverty > 0.3
- Any Black in household (indicator for MEPS oversampling):
Household is not Asian, not poor, at least one Black person
Otherwise
- Age categories for DU reference person:
Less than 25 years old
25–34 years old
35–44 years old
45–64 years old
65 years or older
- Gender of DU reference person:
Male
Female
- Race/ethnicity of DU reference person:
Hispanic
Black, non-Hispanic
Asian (non-Hispanic and non-black)
Otherwise
- Marital status of DU reference person:
Married—spouse in household
Otherwise
- Education level of DU reference person:
No school
Elementary
Some high school
High school graduate or GED
Some college
Bachelor's degree
Graduate school
Unknown
- Family income of DU reference person:
Less than $20,000 and less than $20,000 with no detail given
$20,000–$34,999
$35,000 or greater
$20,000 or higher but no detail given
Unknown
- Employment status of DU reference person:
Employed/working
Unemployed
Not working
Refusal, not ascertained, don't know
- DU reference person needs help with personal care:
Yes
No or refused, not ascertained, don't know
- DU health status:
All members of the DU in good to excellent health
At least one member in fair health, none with poor health
At least one member in poor health
- Number of persons in DU:
One person
Two persons
Three persons
Four persons
Five or more persons
- Census region of DU:
Northeast
Midwest
South
West
- CBSA/MSA status of DU:
In principal city of CBSA/MSA
In CBSA/MSA but not principal city
Not in CBSA/MSA
- CBSA size of DU:
In CBSA with population 500,000 or more
In CBSA with population less than 500,000
Not in CBSA
- Urban/Rural status of DU (1990 Census block designation):
Urban
Rural
- PSU Type:
Self-representing
Non-self-representing
- Telephone number status in NHIS:
Has working telephone and gave phone number
Has working telephone but refused phone number
No working phone
Unknown
- Type of home in NHIS:
House/apt/flat
Other type of dwelling
Missing (not ascertained)
- Time without telephone in NHIS:
3 weeks or less
More than 3 weeks (including no telephone service or no working phone)
No service interruption
Missing (refused, not ascertained, don’t know)
- Interview language in NHIS:
English only
Not English only
Missing (Not ascertained or non-interview household)
- 24. U.S. citizen status in NHIS:
Citizen
Not citizen
Missing (Refused, not ascertained, don’t know)
- Family medical expenses amount in NHIS:
$0
$1 to $499
$500 to $1,999
$2,000 or more
Missing (Refused, not ascertained, don’t know)
- Homeowner status in NHIS:
Owned or being bought
Rented or other
Missing (Refused, not ascertained, don’t know)
- Born in U.S.:
Born in U.S.
Not born in U.S.
Missing (Refused, not ascertained, don’t know)
- Reason did not work last week in NHIS:
Not working for health reasons or disabled
Not working: Retired
Not working other (looking for work, keeping home, school, maternity leave,
vacation, layoff, off-season, other, unknown why not working) or working not
for pay
Working for pay or under 18 years old
Missing (refused, not ascertained, don’t know)
- Number of nights in the hospital last year in NHIS:
Zero nights
1 to 7 nights
8 or more nights
Missing (Refused, not ascertained, don’t know)
- Insurance coverage status in NHIS:
Insured
Uninsured
Missing (refused, not ascertained, don’t know)
Return to Table
of Contents
B.3 Variables Used in Rounds 1 and 3 PIT Family-Level Poststratification
- Family type:
Reference person married and spouse present
Male reference person spouse not present
Female reference person spouse not present
- Race/ethnicity of the reference person:
Hispanic
Black, non-Hispanic
Asian
Other
- Region:
Northeast
Midwest
South
West
- MSA status:
MSA
Non-MSA
- Age categories for the reference person:
<35
35–44
45–64
65 or older
- Number of eligible members of the family:
1 person
2 persons
3 persons
4 persons
5 or more persons
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of Contents
B.4 Variables Used in Round 1 PIT Person-Level Poststratification
- Region containing person (assumed to be the same as for family):
Northeast
Midwest
South
West
- Race/ethnicity of person (assumed to be the same as for family):
Hispanic
Black, non-Hispanic
Asian
Other
- Sex of person:
Male
Female
- Age categories of person:
under 1
1–4
5–9
10–14
15–19
20–24
25–29
30–34
35–44
45–54
55–59
60–64
65–69
70–74
75–80
80+
Return to Table
of Contents
B.5 Variables Used in PIT Round 3 and PIT Final Poststratification
- Race/ethnicity of person:
Hispanic
Black, non-Hispanic
Asian
Other
- Sex of person:
Male
Female
- Region containing person:
Northeast
Midwest
South
West
- MSA status:
MSA
Non-MSA
- Age categories of person:
under 1
1–4
5–9
10–14
15–19
20–24
25–29
30–34
35–44
45–54
55–59
60–64
65–69
70–74
75–80
80+
Return to Table
of Contents
B.6 Variables Used in All FY Person Level Rakings
- Race/ethnicity of person:
Hispanic
Black, non-Hispanic
Asian
Other
- Sex of person:
Male
Female
- Region containing person:
Northeast
Midwest
South
West
- MSA status:
MSA
Non MSA
- Age categories of person:
Under 1
1–19
20–29
30–44
45–64
65+
In addition, the following variable is used in the final raking adjustment
to produce the FY consolidated person weight.
- Poverty status:
Below poverty
100–124 percent
125–199 percent
200–399 percent
400 or more percent
Return to Table
of Contents
B.7 Variables Used in CHAID Analysis to Form Cells for Year 1 FY Person-Level
NR Adjustment (* indicates significant variables in 2007)
- Reluctance to respond in Round 1 interview*:
RU was reluctant to respond
Otherwise
- Age category*:
0–19
20–29
30–44
45–64
65+
- Marital status of family reference person*:
Currently married
Widowed
Divorced
Separated
Never married (includes inapplicable, under 16)
- Family size*:
1 person
2 persons
3 persons
4 persons
5 or more persons
- MSA status*:
MSA
Non-MSA
- Sex*:
Male
Female
- Race/ethnicity*:
Hispanic
Black, non-Hispanic
Asian
Other
- Employment status of reference person*:
Employed
Not employed
Inapplicable, Unknown
- Education level of reference person*:
No degree
High school degree or GED with no college
Some college
College or a higher degree
Inapplicable, Unknown
- Health insurance coverage status of person on interview date*:
Yes
No
Inapplicable
- Census region*:
Northeast
Midwest
South
West
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of Contents
B.8 Variables Used in CHAID Analysis to Form Cells for Year 2 FY Person-Level
NR Adjustment (* indicates significant variables in 2007)
- Reluctance to respond in Round 1 interview*:
RU was reluctant to respond
Otherwise
- Age category*:
0–19
20–29
30–44
45–64
65+
- Marital status of family reference person*:
Currently married
Widowed
Divorced
Separated
Never married (includes inapplicable, under 16)
- Family size*:
1 person
2 persons
3 persons
4 persons
5 or more persons
- MSA status*:
MSA
Non-MSA
- Sex*:
Male
Female
- Race/ethnicity*:
Hispanic
Black, non-Hispanic
Asian
Other
- Education level of reference person*:
No degree
High school degree or GED with no college
Some college
College or a higher degree
Inapplicable, Unknown
- Health insurance coverage status of person on interview date:
Yes
No
Inapplicable
- Census region*:
Northeast
Midwest
South
West
- First respondent indicator:
Yes, First respondent
No, Not first respondent
Nonresponse
- PROXY, proxy respondent indicator:
Respondent is an RU member
Respondent is a proxy
Nonresponse
- Self-perceived health status of the person in year 1*:
Excellent
Very good
Good
Fair
Poor
Unknown/inapplicable
- Total healthcare expenditures of the person in year 1*:
$ 0
$ 1 – 300
$ 301 – 950
$ 951 – 3150
Over $ 3150
Unknown
- Number of office-based provider visits of the person in year
1*:
0
1
2 – 4
5 +
Unknown
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of Contents
B.9 Variables Used in FY Family-level Raking
- Family type on December 31:
Reference person is married, spouse present
Male reference person with no spouse present
Female reference person with no spouse present
- Race/ethnicity of the reference person:
Hispanic
Black, non-Hispanic
Asian
Other
- Poverty status:
Below poverty
100–124 percent
125–199 percent
200–399 percent
400 or more percent
- Region:
Northeast
Midwest
South
West
- MSA status:
MSA
Non MSA
- Number of eligible members of the family on December 31:
1 person
2 persons
3 persons
4 persons
5 or more persons
- Age categories for the reference person:
34 or younger
35–44
45–64
65 or older
Return to Table
of Contents
B.10 Variables Used for SAQ Nonresponse Raking Adjustment
- Region:
Northeast
Midwest
South
West
- MSA status:
MSA
Non MSA
- Family size:
1 person
2 persons
3 or more persons
- Marital status:
Married
Widowed
Divorced/separated
Never married
Under age 16
Missing
- Education:
Less than high school
High school degree
Some college
College degree
Missing
- Health status:
Excellent
Very good
Good, fair, or poor
Other
- Health insurance status:
Yes
No
Missing
- Age on the day of the interview (only individuals 18 or older
are eligible for SAQ):
18–24
25–34
35–44
45–54
55–64
65+
- Sex:
Male
Female
- Race/ethnicity:
Hispanic
Black, non-Hispanic
Asian
Other
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of Contents
Appendix C. Glossary of Selected Terms
Chi-Squared Automatic Interaction Detection (CHAID): CHAID is a software program
with a stepwise statistical procedure that is commonly used to identify subgroups
that differ substantially in their propensity to respond to a survey.
Dwelling Unit (DU): A DU is a house, an apartment, group of rooms, or single
room occupied as separate U.S. civilian noninstitutionalized living quarters
or vacant but intended for occupancy as separate living quarters. An occupied
DU corresponds to a household, using the terminology of the National Health
Interview Survey (NHIS) or the Current Population Survey (CPS). A sample of
NHIS responding households serves as the MEPS sample of DUs (technically, occupied
DUs). A household (DU) can contain one or more families and/or unrelated individuals.
Eligible: The eligibility of a person for MEPS pertains to whether or not
data were to be collected for that person. All of the Key in-scope persons
of a sampled RU are eligible for data collection. The only non-Key persons
eligible for data collection are those who live in an RU with at least one
Key, in-scope person. The eligibility of a non-Key person continues only for
the time that they live with such a person. The only out-of-scope persons eligible
for data collection are those who live with a Key in-scope person, again only
for the time that they live with such a person. Only military persons can meet
this description (for example, a person on full-time active duty military may
live with a spouse who is Key and in-scope).
Family:
1) CPS: A CPS family consists of two or more persons living together in the
same household who are related by blood, marriage, or adoption. Foster children
are not considered a family member in the CPS.
2) MEPS: The definition of a MEPS family is a bit more expansive than that
of the CPS. A MEPS family consists of two or more persons living together in
the same household who are related by blood, marriage, or adoption, as well
as foster children (foster children are not included as members under the CPS
definition of a family) and partners (plus persons related to partners). Partners
are unmarried persons living together who regard themselves as a family unit
(these are not families under the CPS definition). Generally, MEPS RUs with
two or more members are MEPS families. Student RUs are considered a member
of the family of their parent’s RU and thus assigned the same MEPS family
ID as their parents (this is consistent with how the CPS handles students living
away from home).
Full Year (FY): MEPS FY data are released in two phases: a preliminary full
year “Population Characteristics File” is released first which
is superseded a few months later by a final full year “Consolidated File.” The
first file release contains all annual survey data except medical expenditure
and income/tax-related variables which require a longer time to process and
thus are included in the final consolidated file. Moreover, the analytic weights
are not identical in the two separate FY files because income data that are
not available at the initial release are used to refine the weight variables
for the final release. The FY files allow analysts to produce estimates for
the U.S. civilian noninstitutionalized population (i.e., the MEPS target population)
at the person and/or family levels.
In-scope: A member of the civilian, noninstitutionalized population of the
U.S. (MEPS target population) is considered to be in-scope for the survey.
This status can vary within a round since a person may, for example, enter
or return from the military or enter or return from a nursing home during the
reference period of a survey round.
Key: Keyness relates to an individual’s chance of being included in
MEPS. A person is Key if they are linked for sampling purposes to an NHIS responding
household subsampled for inclusion in MEPS. More specifically, a person is
Key if s/he was a member of an NHIS household at the time of the NHIS interview
or became in-scope upon joining an RU with at least one Key member (examples
of the latter situation include newborns and persons returning from military
service, an institution, or living outside the United States). A person who
was in-scope (a member of the civilian, noninstitutionalized U.S. population)
at the time of the NHIS but was not a member of a responding NHIS household
sampled for MEPS is “non-Key”.
Mean Square Error (MSE): The MSE of an estimator  with
respect to the estimated parameter is
defined as  . The MSE is equal
to the sum of
the variance and
the squared bias of the estimator i.e.,  .
Point-in-Time (PIT): MEPS PIT files are produced every year to provide timely
data for estimates related to health insurance and other selected variables
of interest that are available from a single round and require minimal editing.
In the PIT files, Round 1 data for the most recent panel are combined with
Round 3 data from the previous panel. The PIT files can be used to produce
estimates that reflect approximately the first half of the year and/or the
date of first interview in the year.
Poststratification: Poststratification is a procedure used to adjust the sample
weights of responding units so that the totals over various demographic categories
match population totals from another data source.
Raking: Raking procedures involve adjusting the sample weights iteratively
so that the sums over specified margins of the full cross-classification of
characteristics match population sizes from another data source. In contrast
to poststratification, the sum of the sample weights within each cross-classification
cell may not equal the corresponding control totals from the other data source.
Reference Person:
1) MEPS: A reference person is defined for each MEPS family within a DU. This
reference person is usually an RU member 16 years of age or older who either
owns or rents the home. If more than one person meets this description, the
RU respondent identifies one from among them. This is consistent with the
approach used for the Current Population Survey (CPS). If the respondent
is unable to identify a person fitting this definition, the questionnaire
asks for the head of family and this person is then considered the reference
person for that RU.
2) NHIS: The NHIS reference person is defined as the household member 18 years
of age or older who owns or rents the home. If more than one household member
owns or rents the sample unit, or if none of the household members owns or
rents the sample unit, the oldest household member is designated as the reference
person.
Reporting Unit (RU): A MEPS RU is an individual person or a group of persons
in a sampled DU who are related by blood, marriage, adoption, or other familial
association. Regardless of the legal status of their relationship, two persons
living together are treated in MEPS as a single RU if they choose to be identified
as a family unit. Most households contain a single family or a single individual,
although this is not always the case. Examples of households that may be of
the more unusual variety: a single RU consisting of married daughter and her
husband living in the same house (DU) with her parents; two unrelated persons
living in the same apartment (DU) who consider themselves as two independent
entities represent two distinct RUs; and a pair of unmarried people living
in a condominium (DU) who characterize themselves as a single family are treated
as a single RU.
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of Contents
---------------------------
1 In 1996, the first year of MEPS, only one
panel (Panel 1) was fielded, thus the annual data for 1996 were based on this
single panel of data.
2 “yy” in variable names indicates
2-digit year. PIT and longitudinal weight variable names do not have a “yy” component
since PIT files cover the first part of the year while longitudinal files cover
2 years for
a specific panel. The PIT/longitudinal weight variable names do not vary across
years/panels, respectively.
3 For more information regarding the MEPS sample
design, see Ezzati-Rice et al.
4 NHIS indicator for the black and Hispanic households (starting with Panel
12, Asian households are also included in minority status).
5 The control totals for this poststratification
adjustment were derived from NHIS for the adjustment of all MEPS panels except
for Panel 13 when control
totals were derived from the Current Population Survey (CPS) using a different
set of poststratification cells based on region, MSA, and selected characteristics
of a household reference person age, race/ethnicity, marital status, and education.
6 Reference person is an individual identified
as owning or renting the home.
7 Note that the notation c is used to denote
an adjustment cell throughout the report but the cell definition varies from
step to step.
8 A DU is classified as eligible if at least
one member meets the eligibility criterion
for MEPS.
9 Note that the nonresponding cases drop
out of the file after the nonresponse adjustment.
10 See glossary for definitions of families in
NHIS and MEPS.
11 A small proportion of DUs contain more
than one family unit.
12 A reference person is defined for each
family in MEPS and each DU in NHIS. See
glossary for definitions of reference persons in NHIS and MEPS.
13 Because undercoverage was determined
to be negligible for these persons, no poststratification adjustments were
applied to this group in order to
avoid unnecessary
inflation
of the variance of the weights.
14 This poststratification focuses on the portion
of the U.S. population where undercoverage was determined to be most problematic.
15 Responding members of nonresponding families (i.e., families without
response for all members) are assigned their final DU weight as base weight.
16 This removes the issue of multiple chances
of selection being associated with a family.
17 See glossary for a brief description of
CHAID.
18 The purpose of this poststratification is to compensate for potential underrepresentation
of high medical expenditure groups.
19 Adjustment based on data from the Medicare Current Beneficiary Survey.
20 This control total is based on data from
the 1996 MEPS Nursing Home component.
21 Factors are derived using an iterative raking
algorithm.
22 Note that poverty status is not included
here but is included in raking for the final FY Consolidated File.
23 The purpose of this poststratification is
to compensate for potential underrepresentation of these high medical expenditure
groups.
24 A family-level weight is not constructed for the FY Population Characteristics
file.
25 Poverty status is not available at the time
of development of the Population Characteristics file, but is incorporated in
raking for the final weight in the
subsequent FY Consolidated File.
26 The poverty status categories are shown in Appendix B.6.
27 Estimates can be restricted to MEPS families
in-scope on December 31 if appropriate for analytic purposes.
28 For a small number of cases, when the weight
of the reference person is not positive, the weight of the spouse of the reference
person or the weight
of
the oldest member in the family is used.
29 Family weights are assigned to all members
of responding families whose reference person is Key whether the individual
member is Key or not or
in-scope or not
(e.g., a person in the military living with a Key and in-scope family member
is assigned a family weight).
30 Sometimes partitioning of a MEPS family results
in a CPS family where the reference person is non-Key.
31 The DCS weight would generally be applied
if the analysis involves data from both the SAQ and DCS supplements.
32 The SAQ includes questions from the Consumer
Assessment of Health Plans (CAHPS®),
the SF-12, the EuroQol 5D, and attitude items.
33 Rounds 2–3 for the year 1 panel and Rounds 4–5 for the year
2 panel.
34 Panel-specific annual weights are not included
on PUFs.
35 The adjustment was approximately 11% for Panel 11.
36 Panel-specific annual weights are not included
on public use files.
Return to Table of Contents
Suggested Citation:
Machlin S.R., Chowdhury S.R., Ezzati-Rice T., DiGaetano R., Goksel H.,
Wun L.-M., Yu W., Kashihara D. Estimation Procedures for the Medical
Expenditure Panel Survey Household Component. Methodology Report #24.
September 2010. Agency for Healthcare Research and Quality, Rockville,
MD. http://www.meps.ahrq.gov/mepsweb/data_files/publications/mr24/mr24.shtml
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