MEPS Home Medical Expenditure Panel Survey
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MEPS HC-206F:
2018 Outpatient Department Visits

June 2020

The MEPS instrument design changed beginning in Spring of 2018, affecting Panel 23 Round 1, Panel 22 Round 3, and Panel 21 Round 5. For the Full-Year 2017 PUFs, the Panel 22 Round 3 and Panel 21 Round 5 data were transformed to the degree possible to conform to the previous design.

The Full-Year 2018 PUFs are the first year all rounds of data were collected with the re-designed instrument, and no data were transformed to conform to the previous design. In addition, the value -9 NOT ASCERTAINED was removed as an allowable value in the Full-Year 2018 PUFs. Data users should be aware of possible impacts on the data and especially trend analysis for these data years due to the design transition.

Agency for Healthcare Research and Quality
Center for Financing, Access, and Cost Trends
5600 Fishers Lane
Rockville, MD 20857
(301) 427-1406

Table of Contents

A. Data Use Agreement
B. Background
1.0 Household Component
2.0 Medical Provider Component
3.0 Survey Management and Data Collection
C. Technical and Programming Information
1.0 General Information
2.0 Data File Information
2.1 Codebook Structure
2.2 Reserved Codes
2.3 Codebook Format
2.4 Variable Source and Naming Conventions
2.4.1 General
2.4.2 Expenditure and Source of Payment Variables
2.5 File Contents
2.5.1 Survey Administration Variables
2.5.1.1 Person Identifiers (DUID, PID, DUPERSID)
2.5.1.2 Record Identifiers (EVNTIDX, FFEEIDX)
2.5.1.3 Round Indicator (EVENTRN)
2.5.1.4 Panel Indicator (PANEL)
2.5.2 MPC Data Indicator (MPCDATA)
2.5.3 Outpatient Visit Event Variables
2.5.3.1 Visit Details (OPDATEYR-VSTRELCN_M18)
2.5.3.2 Services, Procedures, and Prescription Medicines (LABTEST_M18-MEDPRESC)
2.5.4 Clinical Classification Software Refined
2.5.5 Flat Fee Variables (FFEEIDX, FFOPTYPE, FFBEF18, FFTOT19)
2.5.5.1 Definition of Flat Fee Payments
2.5.5.2 Flat Fee Variable Descriptions
2.5.5.2.1 Flat Fee ID (FFEEIDX)
2.5.5.2.2 Flat Fee Type (FFOPTYPE)
2.5.5.2.3 Counts of Flat Fee Events that Cross Years (FFBEF18, FFTOT19)
2.5.5.3 Caveats of Flat Fee Groups
2.5.6 Expenditure Data
2.5.6.1 Definition of Expenditures
2.5.6.2 Data Editing and Imputation Methodologies of Expenditure Variables
2.5.6.2.1 General Data Editing Methodology
2.5.6.2.2 Imputation Methodologies
2.5.6.2.3 Outpatient Visit Data Editing and Imputation
2.5.6.3 Capitation Imputation
2.5.6.4 Imputation Flag (IMPFLAG)
2.5.6.5 Flat Fee Expenditures
2.5.6.6 Zero Expenditures
2.5.6.7 Discount Adjustment Factor
2.5.6.8 Sources of Payment
2.5.6.9 Imputed Outpatient Expenditure Variables
2.5.6.9.1 Outpatient Facility Expenditure Variables (OPFSF18X-OPFOT18X, OPFXP18X, OPFTC18X)
2.5.6.9.2 Outpatient Physician Expenditures (OPDSF18X – OPDOT18X, OPDXP18X, OPDTC18X)
2.5.6.9.3 Total Expenditures and Charges for Outpatient Visits (OPXP18X, OPTC18X)
2.5.7 Rounding
3.0 Sample Weight (PERWT18F)
3.1 Overview
3.2 Details on Person Weight Construction
3.2.1 MEPS Panel 22 Weight Development Process
3.2.2 MEPS Panel 23 Weight Development Process
3.2.3 The Final Weight for 2018
3.2.4 Coverage
3.3 Using MEPS Data for Trend Analysis
4.0 Strategies for Estimation
4.1 Developing Event-Level Estimates
4.2 Person-Based Estimates for Outpatient Visits
4.3 Variables with Missing Values
4.4 Variance Estimation (VARSTR, VARPSU)
4.4.1 Taylor-series Linearization Method
4.4.2 Balanced Repeated Replication (BRR) Method
5.0 Merging/Linking MEPS Data Files
5.1 Linking to the Person-Level File
5.2 Linking to the Prescribed Medicines File
5.3 Linking to the Medical Conditions File
References
D. Variable-Source Crosswalk

A. Data Use Agreement

Individual identifiers have been removed from the micro-data contained in these files. Nevertheless, under sections 308 (d) and 903 (c) of the Public Health Service Act (42 U.S.C. 242m and 42 U.S.C. 299 a-1), data collected by the Agency for Healthcare Research and Quality (AHRQ) and/or the National Center for Health Statistics (NCHS) may not be used for any purpose other than for the purpose for which they were supplied; any effort to determine the identity of any reported cases is prohibited by law.

Therefore in accordance with the above referenced Federal Statute, it is understood that:

  1. No one is to use the data in this data set in any way except for statistical reporting and analysis; and

  2. If the identity of any person or establishment should be discovered inadvertently, then (a) no use will be made of this knowledge, (b) the Director Office of Management AHRQ will be advised of this incident, (c) the information that would identify any individual or establishment will be safeguarded or destroyed, as requested by AHRQ, and (d) no one else will be informed of the discovered identity; and

  3. No one will attempt to link this data set with individually identifiable records from any data sets other than the Medical Expenditure Panel Survey or the National Health Interview Survey. Furthermore, linkage of the Medical Expenditure Panel Survey and the National Health Interview Survey may not occur outside the AHRQ Data Center, NCHS Research Data Center (RDC) or the U.S. Census RDC network.

By using these data you signify your agreement to comply with the above stated statutorily based requirements with the knowledge that deliberately making a false statement in any matter within the jurisdiction of any department or agency of the Federal Government violates Title 18 part 1 Chapter 47 Section 1001 and is punishable by a fine of up to $10,000 or up to 5 years in prison.

The Agency for Healthcare Research and Quality requests that users cite AHRQ and the Medical Expenditure Panel Survey as the data source in any publications or research based upon these data.

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B. Background

1.0 Household Component

The Medical Expenditure Panel Survey (MEPS) provides nationally representative estimates of health care use, expenditures, sources of payment, and health insurance coverage for the U.S. civilian noninstitutionalized population. The MEPS Household Component (HC) also provides estimates of respondents’ health status, demographic and socio-economic characteristics, employment, access to care, and satisfaction with health care. Estimates can be produced for individuals, families, and selected population subgroups. The panel design of the survey, which includes 5 Rounds of interviews covering 2 full calendar years, provides data for examining person level changes in selected variables such as expenditures, health insurance coverage, and health status. Using computer assisted personal interviewing (CAPI) technology, information about each household member is collected, and the survey builds on this information from interview to interview. All data for a sampled household are reported by a single household respondent.

The MEPS-HC was initiated in 1996. Each year a new panel of sample households is selected. Because the data collected are comparable to those from earlier medical expenditure surveys conducted in 1977 and 1987, it is possible to analyze long-term trends. Each annual MEPS-HC sample size is about 15,000 households. Data can be analyzed at either the person or event-level. Data must be weighted to produce national estimates.

The set of households selected for each panel of the MEPS HC is a subsample of households participating in the previous year’s National Health Interview Survey (NHIS) conducted by the National Center for Health Statistics (NCHS). The NHIS sampling frame provides a nationally representative sample of the U.S. civilian noninstitutionalized population. In 2006, the NHIS implemented a new sample design, which included Asian persons in addition to households with Black and Hispanic persons in the oversampling of minority populations. NHIS introduced a new sample design in 2016 that discontinued oversampling of these minority groups. The linkage of the MEPS to the previous year’s NHIS provides additional data for longitudinal analytic purposes.

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2.0 Medical Provider Component

Upon completion of the household CAPI interview and obtaining permission from the household survey respondents, a sample of medical providers are contacted by telephone to obtain information that household respondents cannot accurately provide. This part of the MEPS is called the Medical Provider Component (MPC) and information is collected on dates of visits, diagnosis and procedure codes, charges and payments. The Pharmacy Component (PC), a subcomponent of the MPC, does not collect charges or diagnosis and procedure codes but does collect drug detail information, including National Drug Code (NDC) and medicine name, as well as date filled and sources and amounts of payment. The MPC is not designed to yield national estimates. It is primarily used as an imputation source to supplement/replace household reported expenditure information.

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3.0 Survey Management and Data Collection

MEPS HC and MPC data are collected under the authority of the Public Health Service Act. Data are collected under contract with Westat, Inc. (MEPS HC) and Research Triangle Institute (MEPS MPC). Data sets and summary statistics are edited and published in accordance with the confidentiality provisions of the Public Health Service Act and the Privacy Act. The National Center for Health Statistics (NCHS) provides consultation and technical assistance.

As soon as data collection and editing are completed, the MEPS survey data are released to the public in staged releases of summary reports, micro data files, and tables via the MEPS website.

Additional information on MEPS is available from the MEPS project manager or the MEPS public use data manager at the Center for Financing, Access, and Cost Trends, Agency for Healthcare Research and Quality, 5600 Fishers Lane, Rockville, MD 20857 (301-427-1406).

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C. Technical and Programming Information

1.0 General Information

This documentation describes one in a series of public use event files from the 2018 Medical Expenditure Panel Survey (MEPS) Household (HC) and Medical Provider Components (MPC). Released as an ASCII data file (with related SAS, SPSS, and Stata programming statements) and SAS transport file, this public use file provides detailed information on outpatient visits for a nationally representative sample of the civilian noninstitutionalized population of the United States and can be used to make estimates of outpatient utilization and expenditures for calendar year 2018. The file contains 60 variables and has a logical record length of 334 with an additional 2-byte carriage return/line feed at the end of each record. As illustrated below, this file consists of MEPS survey data obtained in the 2018 portion of Round 3, and Rounds 4 and 5 for Panel 22, as well as Rounds 1, 2, and the 2018 portion of Round 3 for Panel 23 (i.e., the rounds for the MEPS panels covering calendar year 2018).

This image illustrates that 2018 data were collected in Rounds 3, 4, and 5 of Panel 22, and Rounds 1, 2, and 3 of Panel 23.

Each record on this event file represents a unique outpatient event; that is, an outpatient event reported by the household respondent. Outpatient events reported in Panel 23 Round 3 and known to have occurred after December 31, 2018 are not included on this file.

Annual counts of outpatient visits are based entirely on household reports. Information from the MEPS MPC is used to supplement expenditure and payment data reported by the household, and does not affect use estimates.

Data from this event file can be merged with other MEPS HC data files, for purposes of appending person characteristics such as demographic or health insurance characteristics to each outpatient visit record.

This file can also be used to construct summary variables of expenditures, sources of payment, and related aspects of outpatient visits. Aggregate annual person-level information on the use of outpatient departments and other health services is provided on the MEPS 2018 Full Year Consolidated Data File, where each record represents a MEPS sampled person.

This documentation offers a brief overview of the types and levels of data provided, and the content and structure of the files and the codebook. It contains the following sections:

  • Data File Information
  • Sample Weight
  • Strategies for Estimation
  • Merging/Linking MEPS Data Files
  • References
  • Variable - Source Crosswalk

Any variables not found on this file but released on previous years’ files may have been excluded because they contained only missing data.

For more information on the MEPS HC sample design, see Chowdhury et al (2019). For information on the MEPS MPC design, see S. Cohen, 1998. Copies of the HC and the MPC survey instruments used to collect the information on the Outpatient Department Visits file are available in the Survey Questionnaires section of the MEPS website.

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2.0 Data File Information

The 2018 Outpatient Department Visits public use data set consists of one event-level data file. The file contains characteristics associated with the outpatient (OP) event and imputed expenditure data.

The 2018 outpatient public use data set contains 19,638 outpatient event records; of these records, 19,323 are associated with persons having a positive person-level weight (PERWT18F). This file includes outpatient event records for all household members who resided in eligible responding households and for whom at least one outpatient event was reported. Questions inquired whether someone in the family had a visit to an independent lab or testing facility for x-rays or other tests. An affirmative answer to these questions leads to the creation of an office-based provider event record or an outpatient department event record.

Each record represents one household-reported outpatient event that occurred during calendar year 2018. Outpatient visits known to have occurred after December 31, 2018 are not included on this file. Some household members may have multiple outpatient events and thus will be represented in multiple records on this file. Other household members may have had no outpatient events reported and thus will have no records on this file. These data were collected during the 2018 portion of Round 3, and Rounds 4 and 5 for Panel 22, as well as Rounds 1, 2, and the 2018 portion of Round 3 for Panel 23 of the MEPS HC. The persons represented on this file had to meet either a) or b) below:

  1. Be classified as a key in-scope person who responded for his or her entire period of 2018 eligibility (i.e., persons with a positive 2018 full-year person-level weight (PERWT18F > 0)), or

  2. Be an eligible member of a family all of whose key in-scope members have a positive person-level weight (PERWT18F > 0). (Such a family consists of all persons with the same value for FAMIDYR.) That is, the person must have a positive full-year family-level weight (FAMWT18F>0). Note that FAMIDYR and FAMWT18F are variables on the 2018 Full Year Consolidated Data File.

Persons with no outpatient visit events for 2018 are not included on this event-level OP file but are represented on the person-level 2018 Full Year Population Characteristics file.

Each outpatient visit record includes the following information: date of the visit; whether or not the household member saw the doctor; type of care received; type of services (i.e., lab test, sonogram or ultrasound, x-rays, etc) received; medicines prescribed during the visit; flat fee information; imputed sources of payment; total payment and total charge; a full-year person-level weight; variance strata; and variance PSU.

To append person-level information such as demographic or health insurance coverage to each event record, data from this file can be merged with 2018 MEPS HC person-level data (e.g. Full Year Consolidated or Full Year Population Characteristics files) using the person identifier, DUPERSID. Outpatient visit events on this file can also be linked to the MEPS 2018 Medical Conditions File and to the MEPS 2018 Prescribed Medicines File. Please see Section 5.0 for details on how to merge MEPS data files.

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2.1 Codebook Structure

For most variables on the Outpatient Department events file, both weighted and unweighted frequencies are provided in the accompanying codebook. The exceptions to this are weight variables and variance estimation variables. Only unweighted frequencies of these variables are included in the accompanying codebook file. See the Weights Variables list in Section D, Variable-Source Crosswalk. The codebook and data file sequence list variables in the following order:

  • Unique person identifiers
  • Unique outpatient visit identifiers
  • Outpatient characteristic variables
  • Imputed expenditure variables
  • Weight and variance estimation variables

Note that the person identifier is unique within this data year.

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2.2 Reserved Codes

The following reserved code values are used:

Value Definition
-1 INAPPLICABLE Question was not asked due to skip pattern
-7 REFUSED Question was asked and respondent refused to answer question
-8 DK Question was asked and respondent did not know answer
-15 CANNOT BE COMPUTED Value cannot be derived from data

Generally, values of -1, -7, -8, and -15 for non-expenditure variables have not been edited on this file. The values of -1 and -15 can be edited by the data users/analysts by following the skip patterns in the HC survey questionnaire located on the MEPS website.

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2.3 Codebook Format

This codebook describes an ASCII data set (although the data are also being provided in a SAS transport file).

The following codebook items are provided for each variable:

Identifier Description
Name Variable name
Description Variable descriptor
Format Number of bytes
Type Type of data: numeric (indicated by NUM) or character (indicated by CHAR)
Start Beginning column position of variable in record
End Ending column position of variable in record

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2.4 Variable Source and Naming Conventions

In general, variable names reflect the content of the variable. All imputed/edited variables end with an “X”.

Beginning in 2018, as variable collection, universe, or categories are altered, the variable name will be appended with “_Myy” to indicate in which year the alterations took place. Details about these alterations can be found throughout this document.

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2.4.1 General

Variables on this file were derived from the HC questionnaire itself, the MPC data collection instrument, derived from CAPI, or assigned in sampling. The source of each variable is identified in Section D “Variable – Source Crosswalk” in one of four ways:

  1. Variables derived from CAPI or assigned in sampling are so indicated as “CAPI derived” or “Assigned in sampling,” respectively;

  2. Variables which come from one or more specific questions have those questionnaire sections and question numbers indicated in the “Source” column;

    • FF- Flat Fee section
    • CP- Charge Payment section
    • OP - Outpatient section

  3. Variables constructed from multiple questions using complex algorithms are labeled “Constructed” in the “Source” column; and

  4. Variables which have been edited or imputed are so indicated.

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2.4.2 Expenditure and Source of Payment Variables

The names of the expenditure and source of payment variables follow a standard convention and end in an “X” indicating edited/imputed. Please note that imputed means that a series of logical edits, as well as an imputation process to account for missing data, have been performed on the variable.

The total sum of payments and the 12 source of payment variables are named in the following way:

The first two characters indicate the type of event:

IP - inpatient stay
ER - emergency room visit
HH - home health visit
OM - other medical equipment
OB - office-based visit
OP - outpatient visit
DV - dental visit
RX - prescribed medicine

For expenditure variables on the OP file, the third character indicates whether the expenditure (or amount paid) is associated with the facility (F) or the physician (D).

In the case of the source of payment variables, the fourth and fifth characters indicate:

SF - self or family
MR - Medicare
MD - Medicaid
PV - private insurance
VA - Veterans Administration/CHAMPVA
TR - TRICARE
OF - other federal government
SL - state/local government
WC - Workers’ Compensation
OT - other insurance
OR - other private
OU - other public
XP - sum of payments

In addition, the total charge variable is indicated by TC in the variable name.

The sixth and seventh characters indicate the year (18). The eighth character, “X”, indicates whether the variable is edited/imputed.

For example, OPFSF18X is the edited/imputed amount paid by self or family for the facility portion of the expenditure associated with an outpatient visit.

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2.5 File Contents

2.5.1 Survey Administration Variables
2.5.1.1 Person Identifiers (DUID, PID, DUPERSID)

The dwelling unit ID (DUID) is a seven-digit random number assigned after the case was sampled for MEPS. A three-digit person number (PID) uniquely identifies each person within the dwelling unit. The ten-character variable DUPERSID uniquely identifies each person represented on the file and is the combination of the variables DUID and PID. As part of the new CAPI design, the lengths of the ID variables have changed in the file. The additional 2 bytes in the IDs resulted from adding a 2-digit panel number to the beginning of all the IDs. Analysts wishing to pool data years 2017 and 2018 should add panel numbers to the beginning of Panel 22 Year 2017 ID variables or remove the 2-digit panel number at the beginning of Panel 22 Year 2018 ID variables to ensure they identify the same person. For detailed information on dwelling units and families, please refer to the documentation for the 2018 Full Year Population Characteristics File.

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2.5.1.2 Record Identifiers (EVNTIDX, FFEEIDX)

EVNTIDX uniquely identifies each outpatient event (i.e., each record on the outpatient file) and is the variable required to link outpatient events to data files containing details on conditions and/or prescribed medicines (MEPS 2018 Medical Condition file and MEPS 2018 Prescribed Medicines file, respectively). As part of the new CAPI design, the length of the EVNTIDX has changed to 16 in the file. In addition to the 2-digit panel number added in the beginning, a 2-digit event type number is added to the end. For details on linking see Section 5.0 or the MEPS 2018 Appendix File, HC-206I.

FFEEIDX is a constructed variable that uniquely identifies a flat fee group, that is, all events that were part of a flat fee payment. For example, if a patient receives stitches during an outpatient visit and comes back to have the stitches removed ten days later in a follow-up outpatient visit, both visits are covered under one flat fee dollar amount. These two events (the initial outpatient visit and the subsequent outpatient visit) would have the same value for FFEEIDX. A “mixed” flat fee group could contain both outpatient and office-based visits. Only outpatient and office-based events are allowed in a mixed bundle. Please note that FFEEIDX should be used to link up the outpatient and office-based events in order to determine the full set of events that are part of a flat fee group.

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2.5.1.3 Round Indicator (EVENTRN)

EVENTRN indicates the round in which the outpatient event was reported. Please note: Rounds 3, 4, and 5 are associated with MEPS survey data collected from Panel 22. Likewise, Rounds 1, 2, and 3 are associated with data collected from Panel 23.

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2.5.1.4 Panel Indicator (PANEL)

PANEL is a constructed variable used to specify the panel number for the person. PANEL will indicate either Panel 22 or Panel 23 for each person on the file. Panel 22 is the panel that started in 2017, and Panel 23 is the panel that started in 2018.

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2.5.2 MPC Data Indicator (MPCDATA)

MPCDATA is a constructed variable that indicates whether or not MPC data were collected for the outpatient visit. While all outpatient events are sampled into the Medical Provider Component, not all outpatient event records have MPC data associated with them. This is dependent upon the cooperation of the household respondent to provide permission forms to contact the outpatient facility as well as the cooperation of the outpatient facility to participate in the survey.

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2.5.3 Outpatient Visit Event Variables

This file contains variables describing outpatient events reported by respondents in the Outpatient Department section of the MEPS HC questionnaire. The questionnaire contains specific probes for determining details about the outpatient visit. These variables have not been edited.

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2.5.3.1 Visit Details (OPDATEYR-VSTRELCN_M18)

When a person reported having had a visit to a hospital outpatient department or special clinic, the year and month of the outpatient visit was reported (OPDATEYR and OPDATEMM). It also establishes whether the person saw or spoke to a medical doctor (SEEDOC_M18). If the person did not see a specialty doctor (DRSPLTY_M18), or, if the person did not see a physician (i.e., medical doctor), the respondent was asked to identify the type of medical person that was seen (MEDPTYPE_M18). The type of care the person received (VSTCTGRY), and whether or not the visit was related to a specific condition (VSTRELCN_M18) were also determined. Note that response categories with small frequencies may have been recoded to other categories for confidentiality reasons. Starting in 2018, due to design changes, the variable SEETLKPV is removed.

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2.5.3.2 Services, Procedures, and Prescription Medicines (LABTEST_M18-MEDPRESC)

Services received during the visit included whether or not the person received lab tests (LABTEST_M18), a sonogram or ultrasound (SONOGRAM_M18), x-rays (XRAYS_M18), a mammogram (MAMMOG_M18), an MRI or CAT scan (MRI_M18), an electrocardiogram / an electroencephalogram (EKG_M18), and a vaccination (RCVVAC_M18). Minimal editing was done across treatment, services, and procedures to ensure consistency across “inapplicable,” “don’t know,” “refused,” and “no services received” values. Due to design changes, beginning in 2017, EEG was combined with EKG; ANESTH (This visit did p receive anesthesia) and THRTSWAB (This visit did p have a throat swab) were removed. Beginning in 2018, OTHSVCE is removed. Whether or not a surgical procedure was performed during the visit was asked (SURGPROC).

Finally, the questionnaire determined if a medicine was prescribed for the person during the visit (MEDPRESC). For a repeat visit event group, if a prescribed medicine is linked to the stem event (MEDPRESC=1), then the value of MEDPRESC is copied to the leaf events without linking the leaf events to the prescribed medicine. MEDPRESC=1 was recoded to -15 for all leaf events.

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2.5.4 Clinical Classification Software Refined

Information on household-reported medical conditions (ICD-10-CM condition codes) and aggregated clinically meaningful categories generated using Clinical Classification Software Refined (CSSR) for each outpatient visit are not provided on this file. For information on ICD-10-CM condition codes and associated CCSR codes, see the MEPS 2018 Medical Conditions file.

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2.5.5 Flat Fee Variables (FFEEIDX, FFOPTYPE, FFBEF18, FFTOT19)
2.5.5.1 Definition of Flat Fee Payments

A flat fee is the fixed dollar amount a person is charged for a package of health care services provided during a defined period of time. Examples would be: an obstetrician’s fee covering a normal delivery, as well as pre- and post-natal care; or a surgeon’s fee covering surgical procedure along with post-surgical care. A flat fee group is the set of medical services (i.e., events) that are covered under the same flat fee payment. The flat fee groups represented on this file include flat fee groups where at least one of the health care events, as reported by the HC respondent, occurred during 2018. By definition a flat fee group can span multiple years. Furthermore, a single person can have multiple flat fee groups.

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2.5.5.2 Flat Fee Variable Descriptions
2.5.5.2.1 Flat Fee ID (FFEEIDX)

As noted earlier in Section 2.5.1.2 “Record Identifiers,” the variable FFEEIDX uniquely identifies all events that are part of the same flat fee group for a person. On any 2018 MEPS event file, every event that was a part of a specific flat fee group will have the same value for FFEEIDX. Note that prescribed medicine and home health events are never included in a flat fee group and FFEEIDX is not a variable on those event files.

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2.5.5.2.2 Flat Fee Type (FFOPTYPE)

FFOPTYPE indicates whether the 2018 outpatient visit is the “stem” or “leaf” of a flat fee group. A stem (records with FFOPTYPE = 1) is the initial medical service (event) which is followed by other medical events that are covered under the same flat fee payment. The leaves of the flat fee group (records with FFOPTYPE = 2) are those medical events that are tied back to the initial medical event (the stem) in the flat fee group. These “leaf” records have their expenditure variables set to zero. For the outpatient visits that are not part of a flat fee payment, the FFOPTYPE is set to -1, “INAPPLICABLE.”

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2.5.5.2.3 Counts of Flat Fee Events that Cross Years (FFBEF18, FFTOT19)

As described above, a flat fee payment covers multiple events and the multiple events could span multiple years. For situations where the outpatient visit occurred in 2018 as a part of a group of events, and some of the events occurred before or after 2018, counts of the known events are provided on the outpatient visit record. Variables indicating events that occurred before or after 2018 are as follows:

  • FFBEF18 – total number of pre-2018 events in the same flat fee group as the 2018 outpatient visit. This count would not include the 2018 outpatient visit(s).

  • FFTOT19 – the number of 2019 outpatient visits expected to be in the same flat fee group as the outpatient visit record that occurred in 2018.

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2.5.5.3 Caveats of Flat Fee Groups

There are 290 outpatient visits that are identified as being part of a flat fee payment group. In general, every flat fee group should have an initial visit (stem) and at least one subsequent visit (leaf). There are some situations where this is not true. For some of these flat fee groups, the initial visit reported occurred in 2018 but the remaining visits that were part of this flat fee group occurred in 2019. In this case, the 2018 flat fee group represented on this file would consist of one event (the stem). The 2018 events that are part of this flat fee group are not represented on the file. Similarly, the household respondent may have reported a flat fee group where the initial visit began in 2017 but subsequent visits occurred during 2018. In this case, the initial visit would not be represented on the file. This 2018 flat fee group would then only consist of one or more leaf records and no stem. Another reason for which a flat fee group would not have a stem and at least one leaf record is that the stem or leaves could have been reported as different event types. Outpatient and office-based medical provider visits are the only two event types allowed in a single flat fee group. The stem may have been reported as an outpatient department visit and the leaves may have been reported as office-based medical provider visits. Please note that the crosswalk in this document lists all possible flat fee variables.

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2.5.6 Expenditure Data
2.5.6.1 Definition of Expenditures

Expenditures on this file refer to what is paid for outpatient services. More specifically, expenditures in MEPS are defined as the sum of payments for care received for each outpatient visit, including out-of-pocket payments and payments made by private insurance, Medicaid, Medicare, and other sources. The definition of expenditures used in MEPS differs slightly from its predecessors, the 1987 NMES and 1977 NMCES surveys, where “charges” rather than sum of payments were used to measure expenditures. This change was adopted because charges became a less appropriate proxy for medical expenditures during the 1990s due to the increasingly common practice of discounting. Although measuring expenditures as the sum of payments incorporates discounts in the MEPS expenditure estimates, the estimates do not incorporate any payment not directly tied to specific medical care visits, such as bonuses or retrospective payment adjustments paid by third party payers. Currently, charges associated with uncollected liability, bad debt, and charitable care (unless provided by a public clinic or hospital) are not counted as expenditures because there are no payments associated with those classifications. For details on expenditure definitions, please reference the following: “Informing American Health Care Policy” (Monheit, et al., 1999). AHRQ has developed factors to apply to the 1987 NMES expenditure data to facilitate longitudinal analysis. These factors can be accessed via the CFACT data center. For more information, see the data center section of the MEPS website.

Expenditure data related to outpatient visits are broken out by facility and separately billing doctor expenditures. This file contains six categories of expenditure variables per visit: basic hospital outpatient facility expenses; expenses for doctors who billed separately from the outpatient facility for any services provided during the outpatient visit; total expenses, which is the sum of the facility and physician expenses; facility charge; physician charge; and total charges, which is the sum of the facility and physician charges. If examining trends in MEPS expenditures, please refer to Section 3.3 for more information.

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2.5.6.2 Data Editing and Imputation Methodologies of Expenditure Variables

The expenditure data included on this file were derived from both the MEPS Household (HC) and the Medical Provider Components (MPC). The MPC contacted medical providers identified by household respondents. The charge and payment data from medical providers were used in the expenditure imputation process to supplement missing household data. For all outpatient visits, MPC data were used if available; otherwise, HC data were used. Missing data for outpatient visits where HC data were not complete and MPC data were not collected, or MPC data were not complete, were derived through the imputation process.

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2.5.6.2.1 General Data Editing Methodology

Logical edits were used to resolve internal inconsistencies and other problems in the HC and MPC survey-reported data. The edits were designed to preserve partial payment data from households and providers, and to identify actual and potential sources of payment for each household-reported event. In general, these edits accounted for outliers, co-payments or charges reported as total payments, and reimbursed amounts that were reported as out-of-pocket payments. In addition, edits were implemented to correct for misclassifications between Medicare and Medicaid and between Medicare HMOs and private HMOs as payment sources. These edits produced a complete vector of expenditures for some events, and provided the starting point for imputing missing expenditures in the remaining events.

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2.5.6.2.2 Imputation Methodologies

The predictive mean matching imputation method was used to impute missing expenditures. This procedure uses regression models (based on events with completely reported expenditure data) to predict total expenses for each event. Then, for each event with missing payment information, a donor event with the closest predicted payment with the same pattern of expected payment sources as the event with missing payment was used to impute the missing payment value. The weighted sequential hot-deck procedure was used to impute the missing total charges. This procedure uses survey data from respondents to replace missing data while taking into account the persons’ weighted distribution in the imputation process. The imputations for the flat fee events were carried out separately from the simple events.

Expenditures for services provided by separately billing doctors in hospital settings were also edited and imputed. These expenditures are shown separately from hospital facility charges for hospital inpatient, outpatient, and emergency room care.

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2.5.6.2.3 Outpatient Visit Data Editing and Imputation

Facility expenditures for outpatient services were developed in a sequence of logical edits and imputations. “Household” edits were applied to sources and amounts of payment for all events reported by HC respondents. “MPC” edits were applied to provider-reported sources and amounts of payment for records matched to household-reported events. Both sets of edits were used to correct obvious errors in the reporting of expenditures. After the data from each source were edited, a decision was made as to whether household- or MPC-reported information would be used in the final editing and predictive mean matching imputations for missing expenditures. The general rule was that MPC data would be used where a household-reported event corresponded to an MPC-reported event (i.e., a matched event), since providers usually have more complete and accurate data on sources and amounts of payment than households.

One of the more important edits separated flat fee events from simple events. This edit was necessary because groups of events covered by a flat fee (i.e., a flat fee bundle) were edited and imputed separately from individual events covered by a single charge (i.e., simple events). (See Section 2.5.5 for more details on flat fee groups).

Logical edits also were used to sort each event into a specific category for the imputations. Events with complete expenditures were flagged as potential donors for the predictive mean matching imputations, while events with missing expenditure data were assigned to various recipient categories. Each event with missing expenditure data was assigned to a recipient category based on the extent of its missing charge and expenditure data. For example, an event with a known total charge but no expenditure information was assigned to one category, while an event with a known total charge and partial expenditure information was assigned to a different category. Similarly, events without a known total charge and no or partial expenditure information were assigned to various recipient categories.

The logical edits produced eight recipient categories in which all events had a common extent of missing data. However, for predictive mean matching imputations, the recipients were grouped into four categories based on the known status of total charge and the sources of payment: 1. Known charge but unknown payment status of at least one potential paying source; 2. Unknown charge and unknown payment status of at least one potential paying source; 3. Known charge and known status of all payment sources; and 4. Unknown charge and known status of all payment sources. Separate predictive mean matching imputations were performed on events in each recipient group. For outpatient events, the donor pool was restricted to events with complete expenditures from the MPC.

The donor pool included “free events” because, in some instances, providers are not paid for their services. These events represent charity care, bad debt, provider failure to bill, and third party payer restrictions on reimbursement in certain circumstances. If free events were excluded from the donor pool, total expenditures would be over-counted because the distribution of free events among complete events (donors) would not be represented among incomplete events (recipients).

For office-based and outpatient events, the donor pool also included events originally reported by providers as paid on a capitated basis. To obtain the fee-for-service (FFS) equivalent payments for these capitated events, a “capitation imputation” was implemented (see the next section). Once imputed with the FFS equivalent payments, these events became donors for all other incomplete events, particularly for events reported by the household as services covered under managed care plans.

Expenditures for services provided by separately billing doctors in hospital settings were also edited and imputed. These expenditures are shown separately from hospital facility charges for hospital inpatient, outpatient, and emergency room.

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2.5.6.3 Capitation Imputation

The weighted sequential hot-deck procedure was used to estimate expenditures at the event-level for events that were paid on a per-month per-person (capitated) basis. The capitation imputation procedure was designed as a reasonable approach to complete event-level expenditures for persons in non-fee for service managed care plans. HMO events reported in the MPC as covered by capitation arrangements were imputed using similar HMO events paid on a fee-for-service, with total charge as a key variable. Then this fully completed set of MPC events was used in the donor pool for the main imputation process for cases in HMOs. By using this strategy, capitated HMO events were imputed as if the provider were reimbursed from the HMO on a discounted fee-for-service basis.

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2.5.6.4 Imputation Flag (IMPFLAG)

IMPFLAG is a six-category variable that indicates if the event contains complete Household Component (HC) or Medical Provider Component (MPC) data, was fully or partially imputed, or was imputed in the capitated imputation process (for OP and OB events only). The following list identifies how the imputation flag is coded; the categories are mutually exclusive.

  • IMPFLAG = 0 not eligible for imputation (includes zeroed out and flat fee leaf events)

  • IMPFLAG = 1 complete HC data

  • IMPFLAG = 2 complete MPC data

  • IMPFLAG = 3 fully imputed

  • IMPFLAG = 4 partially imputed

  • IMPFLAG = 5 complete MPC data through capitation imputation

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2.5.6.5 Flat Fee Expenditures

The approach used to count expenditures for flat fees was to place the expenditure on the first visit of the flat fee group. The remaining visits have zero facility payments, physician’s expenditures may still be present. Thus, if the first visit in the flat fee group occurred prior to 2018, all of the events that occurred in 2018 will have zero payments. Conversely, if the first event in the flat fee group occurred at the end of 2018, the total expenditure for the entire flat fee group will be on that event, regardless of the number of events it covered after 2018. See Section 2.5.5 for details on the flat fee variables.

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2.5.6.6 Zero Expenditures

There are some medical events reported by respondents where the payments were zero. Zero payment events can occur in MEPS for the following reasons: (1) the visit was covered under a flat fee arrangement (flat fee payments are included only on the first event covered by the arrangement), (2) there was no charge for a follow-up visit, (3) the provider was never paid directly for services provided by an individual, insurance plan, or other source, (4) the charges were included in another bill, or (5) the event was paid through government or privately funded research or clinical trials.

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2.5.6.7 Discount Adjustment Factor

An adjustment was also applied to some HC-reported expenditure data because an evaluation of matched HC/MPC data showed that respondents who reported that charges and payments were equal were often unaware that insurance payments for the care had been based on a discounted charge. To compensate for this systematic reporting error, a weighted sequential hot-deck imputation procedure was implemented to determine an adjustment factor for HC-reported insurance payments when charges and payments were reported to be equal. As for the other imputations, selected predictor variables were used to form groups of donor and recipient events for the imputation process.

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2.5.6.8 Sources of Payment

In addition to total expenditures, variables are provided which itemize expenditures according to major source of payment categories. These categories are:

  1. Out-of-pocket by User (self) or Family - includes any deductible, coinsurance, and copayment amounts not covered by other sources, as well as payments for services and providers not covered by the person’s insurance or other sources,
  2. Medicare,
  3. Medicaid,
  4. Private Insurance,
  5. Veterans Administration/CHAMPVA, excluding TRICARE,
  6. TRICARE,
  7. Other Federal Sources – includes Indian Health Service, military treatment facilities, and other care by the federal government,
  8. Other State and Local Source – includes community and neighborhood clinics, state and local health departments, and state programs other than Medicaid,
  9. Workers’ Compensation, and
  10. Other Unclassified Sources – includes sources such as automobile, homeowner’s, and liability insurance, and other miscellaneous or unknown sources.

Two additional source of payment variables were created to classify payments for events with apparent inconsistencies between insurance coverage and sources of payment based on data collected in the survey. These variables include:

  1. Other Private – any type of private insurance payments reported for persons not reported to have any private health insurance coverage during the year as defined in MEPS, and
  2. Other Public – Medicare/Medicaid payments reported for persons who were not reported to be enrolled in the Medicare/Medicaid program at any time during the year.

Though these two sources are relatively small in magnitude, data users/analysts should exercise caution when interpreting the expenditures associated with these two additional sources of payment. While these payments stem from apparent inconsistent responses to health insurance and source of payment questions in the survey, some of these inconsistencies may have logical explanations. For example, private insurance coverage in MEPS is defined as having a major medical plan covering hospital and physician services. If a MEPS sampled person did not have such coverage but had a single service type insurance plan (e.g., dental insurance) that paid for a particular episode of care, those payments may be classified as “other private”. Some of the “other public” payments may stem from confusion between Medicaid and other state and local programs or may be from persons who were not enrolled in Medicaid, but were presumed eligible by a provider who ultimately received payments from the public payer.

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2.5.6.9 Imputed Outpatient Expenditure Variables

This file contains two sets of imputed expenditure variables: facility expenditures and physician expenditures.

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2.5.6.9.1 Outpatient Facility Expenditure Variables (OPFSF18X-OPFOT18X, OPFXP18X, OPFTC18X)

Outpatient visit expenses include all expenses for treatment, services, tests, diagnostic and laboratory work, x-rays, and similar charges, as well as any physician services included in the hospital outpatient visit charge.

OPFSF18X – OPFOT18X are the 12 sources of payment. The 12 sources of payment are: self/family (OPFSF18X), Medicare (OPFMR18X), Medicaid (OPFMD18X), private insurance (OPFPV18X), Veterans Administration/CHAMPVA (OPFVA18X), TRICARE (OPFTR18X), other federal sources (OPFOF18X), state and local (non-federal) government sources (OPFSL18X), Workers’ Compensation (OPFWC18X), other private insurance (OPFOR18X), other public insurance (OPFOU18X), and other insurance (OPFOT18X). OPFXP18X is the sum of the 12 sources of payment for the outpatient facility expenditures, and OPFTC18X is the total charge. Please note that where an outpatient visit record is linked to a hospital inpatient stay record, all facility sources of payment variables, as well as OPFTC18X have been zeroed out.

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2.5.6.9.2 Outpatient Physician Expenditures (OPDSF18X – OPDOT18X, OPDXP18X, OPDTC18X)

Separately billing doctor (SBD) expenses typically cover services provided to patients in hospital settings by providers like anesthesiologists, radiologists, and pathologists, whose charges are often not included in the outpatient facility bill.

For physicians who bill separately (i.e., outside the outpatient facility bill), a separate data collection effort within the Medical Provider Component was performed to obtain the same set of expenditure information from each separately billing doctor. It should be noted that there could be several separately billing doctors associated with a medical event. For example, an outpatient visit could have a radiologist and a pathologist associated with it. If their services are not included in the outpatient visit bill then this is one medical event with 2 separately billing doctors. The imputed expenditure information associated with the separately billing doctors was summed to the event-level and is provided on the file. OPDSF18X – OPDOT18X are the 12 sources of payment, OPDXP18X is the sum of the 12 sources of payments, and OPDTC18X is the physician(s) total charge.

Data users/analysts need to take into consideration whether to analyze facility and SBD expenditures separately, combine them within service categories, or collapse them across service categories (e.g., combine SBD expenditures with expenditures for physician visits to offices and/or outpatient departments).

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2.5.6.9.3 Total Expenditures and Charges for Outpatient Visits (OPXP18X, OPTC18X)

Data users/analysts interested in total expenditures should use the variable OPXP18X, which includes both facility and physician amounts. Those interested in total charges should use the variable OPTC18X, which includes both facility and physician charges (see Section 2.5.6.1 for an explanation of the “charge” concept).

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2.5.7 Rounding

Expenditure variables have been rounded to the nearest penny. Person-level expenditure information released on the MEPS 2018 Person-Level Use and Expenditure File were rounded to the nearest dollar. It should be noted that using the MEPS 2018 event files to create person-level totals will yield slightly different totals than those found on the person-level expenditure file. These differences are due to rounding only. Moreover, in some instances, the number of persons having expenditures on the event files for a particular source of payment may differ from the number of persons with expenditures on the person-level expenditure file for that source of payment. This difference is also an artifact of rounding only.

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3.0 Sample Weight (PERWT18F)

3.1 Overview

There is a single full year person-level weight (PERWT18F) assigned to each record for each key, in-scope person who responded to MEPS for the full period of time that he or she was in-scope during 2018. A key person was either a member of a responding NHIS household at the time of interview or joined a family associated with such a household after being out-of-scope at the time of the NHIS (the latter circumstance includes newborns as well as those returning from military service, an institution, or residence in a foreign country). A person is in-scope whenever he or she is a member of the civilian noninstitutionalized portion of the U.S. population.

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3.2 Details on Person Weight Construction

The person-level weight PERWT18F was developed in several stages. Person-level weights for Panel 22 and Panel 23 were created separately. The weighting process for each panel included an adjustment for nonresponse over time and calibration to independent population figures. The calibration was initially accomplished separately for each panel by raking the corresponding sample weights for those in-scope at the end of the calendar year to Current Population Survey (CPS) population estimates based on six variables. The six variables used in the establishment of the initial person-level control figures were: educational attainment of the reference person (no degree, high school/GED no college, some college, bachelor’s degree or higher); census region (Northeast, Midwest, South, West); MSA status (MSA, non-MSA); race/ethnicity (Hispanic; Black, non-Hispanic; Asian, non-Hispanic; and other); sex; and age. A 2018 composite weight was then formed by multiplying each weight from Panel 22 by the factor .490 and each weight from Panel 23 by the factor .510. The choice of factors reflected the relative sample sizes of the two panels, helping to limit the variance of estimates obtained from pooling the two samples. The composite weight was raked to the same set of CPS-based control totals. When the poverty status information derived from income variables became available, a final raking was undertaken, establishing control figures reflecting poverty status rather than educational attainment. Thus, control totals were established using poverty status (five categories: below poverty, from 100 to 125 percent of poverty, from 125 to 200 percent of poverty, from 200 to 400 percent of poverty, at least 400 percent of poverty) as well as the other five variables previously used in the weight calibration.

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3.2.1 MEPS Panel 22 Weight Development Process

The person-level weight for MEPS Panel 22 was developed using the 2017 full year weight for an individual as a “base” weight for survey participants present in 2017. For key, in-scope members who joined an RU some time in 2018 after being out-of-scope in 2017, the initially assigned person-level weight was the corresponding 2017 family weight. The weighting process included an adjustment for person-level nonresponse over Rounds 4 and 5 as well as raking to population control totals for December 2018 for key, responding persons in-scope on December 31, 2018. These control figures were derived by scaling back the population distribution obtained from the March 2019 CPS to reflect the December 31, 2018 estimated population total (estimated based on Census projections for January 1, 2019). Variables used for person-level raking included: educational attainment of the reference person (no degree, high school/GED no college, some college, bachelor’s degree or higher); census region (Northeast, Midwest, South, West); MSA status (MSA, non-MSA); race/ethnicity (Hispanic; Black, non-Hispanic; Asian, non-Hispanic; and other); sex; and age. (Poverty status is not included in this version of the MEPS full year database because of the time required to process the income data collected and then assign persons to a poverty status category). The final weight for key, responding persons who were not in-scope on December 31, 2018 but were in-scope earlier in the year was the person weight after the nonresponse adjustment.

Note that the 2017 full-year weight that was used as the base weight for Panel 22 was derived as follows; adjustment of the MEPS Round 1 weight for nonresponse over the remaining data collection rounds in 2017; and raking the resulting nonresponse adjusted weight to December 2017 population control figures.

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3.2.2 MEPS Panel 23 Weight Development Process

The person-level weight for MEPS Panel 23 was developed using the 2018 MEPS Round 1 person-level weight as a “base” weight. For key, in-scope members who joined an RU after Round 1, the Round 1 family weight served as a “base” weight. The weighting process included an adjustment for nonresponse over the remaining data collection rounds in 2018 as well as raking to the same population control figures for December 2018 used for the MEPS Panel 22 weights for key, responding persons in-scope on December 31, 2018. The same six variables employed for Panel 22 raking (educational attainment of the reference person, census region, MSA status, race/ethnicity, sex, and age) were used for Panel 23 raking. Again, the final weight for key, responding persons who were not in-scope on December 31, 2018 but were in-scope earlier in the year was the person weight after the nonresponse adjustment.

Note that the MEPS Round 1 weights for Panel 23 incorporated the following components: the original household probability of selection for the NHIS; proportion of the NHIS sample reserved for MEPS; adjustment for NHIS nonresponse; the probability of selection of NHIS responding households for MEPS; an adjustment for nonresponse at the dwelling unit level for Round 1; and poststratification to U.S. civilian noninstitutionalized population estimates at the family and person level obtained from the corresponding March CPS databases.

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3.2.3 The Final Weight for 2018

The final raking of those in-scope at the end of the year has been described above. In addition, the composite weights of two groups of persons who were out-of-scope on December 31, 2018 were adjusted for expected undercoverage. Specifically, the weights of those who were in-scope some time during the year, out-of-scope on December 31, and entered a nursing home during the year and still residing in a nursing home at the end of the year were adjusted to compensate for expected undercoverage for this subpopulation. The weights of persons who died while in-scope during 2018 were poststratified to corresponding estimates derived using data obtained from the Medicare Current Beneficiary Survey (MCBS) and Vital Statistics information provided by the National Center for Health Statistics (NCHS). Separate decedent control totals were developed for the “65 and older” and “under 65” civilian noninstitutionalized populations.

Overall, the weighted population estimate for the civilian noninstitutionalized population for December 31, 2018 is 322,920,490 (PERWT18F>0 and INSC1231=1). The sum of person-level weights across all persons assigned a positive person-level weight is 326,327,888.

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3.2.4 Coverage

The target population for MEPS in this file is the 2018 U.S. civilian noninstitutionalized population. However, the MEPS sampled households are a subsample of the NHIS households interviewed in 2016 (Panel 22) and 2017 (Panel 23). New households created after the NHIS interviews for the respective panels and consisting exclusively of persons who entered the target population after 2016 (Panel 22) or after 2017 (Panel 23) are not covered by MEPS. Neither are previously out-of-scope persons who join an existing household but are unrelated to the current household residents. Persons not covered by a given MEPS panel thus include some members of the following groups: immigrants; persons leaving the military; U.S. citizens returning from residence in another country; and persons leaving institutions. The set of uncovered persons constitutes only a small segment of the MEPS target population.

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3.3 Using MEPS Data for Trend Analysis

MEPS began in 1996, and the utility of the survey for analyzing health care trends expands with each additional year of data; however, there are a variety of methodological and statistical considerations when examining trends over time using MEPS. Tests of statistical significance should be conducted to assess the likelihood that observed trends may be attributable to sampling variation. The length of time being analyzed should also be considered. In particular, large shifts in survey estimates over short periods of time (e.g. from one year to the next) that are statistically significant should be interpreted with caution unless they are attributable to known factors such as changes in public policy, economic conditions, or MEPS survey methodology.

With respect to methodological considerations, in 2013 MEPS introduced an effort to obtain more complete information about health care utilization from MEPS respondents with full implementation in 2014. This effort likely resulted in improved data quality and a reduction in underreporting starting in FY 2014, and could have some modest impact on analyses involving trends in utilization across years. The change in the NHIS sample design in 2016 could also potentially affect trend analyses. For example, coverage of the MEPS target population would be expected to have increased, so subpopulations whose coverage rates were particularly increased would have increased contributions from undercovered portions of their subpopulation.

Another change with the potential to affect trend analyses involved modifications to the MEPS instrument design and data collection process. These were introduced in the Spring of 2018 and thus affected data beginning with Round 1 of Panel 23, Round 3 of Panel 22, and Round 5 of Panel 21. Since the Full Year 2017 PUFs were established from data collected in Rounds 1-3 of Panel 22 and Rounds 3-5 of Panel 21, they reflected two different instrument designs. In order to mitigate the effect of such differences within the same full year file, the Panel 22, Round 3 data and the Panel 21 Round 5 data were transformed to make them as consistent as possible with data collected under the previous design. The changes were designed to make the data collection effort more efficient and easy to administer. In addition, expectations were that data on some items, such as those related to health care events, would be more complete with the potential of identifying more events. Increases in service use reported since the implementation of these changes are consistent with these expectations.

There are also statistical factors to consider in interpreting trend analyses. Looking at changes over longer periods of time can provide a more complete picture of underlying trends. Analysts may wish to consider using techniques to evaluate, smooth, or stabilize analyses of trends using MEPS data such as comparing pooled time periods (e.g. 1996-97 versus 2011-13), working with moving averages, or using modeling techniques with several consecutive years of MEPS data to test the fit of specified patterns over time. Finally, researchers should be aware of the impact of multiple comparisons on Type I error. Without making appropriate allowance for multiple comparisons, undertaking numerous statistical significance tests of trends increases the likelihood of concluding that a change has taken place when one has not.

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4.0 Strategies for Estimation

4.1 Developing Event-Level Estimates

The data in this file can be used to develop national 2018 event-level estimates for the U.S. civilian noninstitutionalized population on outpatient visits as well as expenditures, and sources of payment for these visits. Estimates of total visits are the sum of the weight variable (PERWT18F) across relevant event records while estimates of other variables must be weighted by PERWT18F to be nationally representative. The tables below contain event-level estimates for selected variables.

Selected Event-Level Estimates

Outpatient Visits

Estimate of Interest Variable Name Estimate (SE) Estimate Excluding Zero Payment Events (SE)*
Total number of outpatient visits (in millions) PERWT18F 203.4 (10.36) 197.3 (10.11)
Total number of in-person visits to doctor (SEEDOC_M18=1, in millions) PERWT18F 96.5 (5.19) 93.9 (5.06)
Proportion of outpatient visits with expenditures > 0* OPXP18X 0.970 (0.0061) -------------


Outpatient Expenditures

Estimate of Interest Variable Name Estimate (SE) Estimate Excluding Zero Payment Events (SE)*
Mean total payments per visit (all sources) OPXP18X $878 ($33.1) $905 ($34.4)
Mean out-of-pocket payment per visit OPDSF18X +OPFSF18X $63 ($4.1) $65 ($4.3)
Mean proportion of total expenditures paid by private insurance per visit (OPDPV18X+OPFPV18X) /OPXP18X ------------- 0.350 (0.0139)


Expenditures: Physician Visits

Estimate of Interest Variable Name Estimate (SE) Estimate Excluding Zero Payment Events (SE)*
Mean total payments per visit where person saw medical doctor OPXP18X $1,307 ($58.7) $1,343 ($60.2)
Mean out-of-pocket payment per visit where person saw medical doctor OPDSF18X +OPFSF18X $88 ($7.6) $90 ($7.8)
Mean proportion of total expenditures per visit paid by private insurance where person saw medical doctor (OPDPV18X+OPFPV18X)/OPXP18X ------------- 0.355 (0.0182)

* Zero payment events can occur in MEPS for the following reasons: (1) the visit was covered under a flat fee arrangement (flat fee payments are included only on the first event covered by the arrangement), (2) there was no charge for a follow-up visit, (3) the provider was never paid directly for services provided by an individual, insurance plan, or other source, (4) the charges were included in another bill, or (5) the event was paid through government or privately funded research or clinical trials.

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4.2 Person-Based Estimates for Outpatient Visits

To enhance analyses of hospital outpatient visits, analysts may link information about outpatient visits by sample persons in this file to the annual full year consolidated file (which has data for all MEPS sample persons), or conversely, link person-level information from the full year consolidated file to this event-level file (see Section 5 below for more details). Both this file and the full year consolidated file may be used to derive estimates for persons with outpatient care and annual estimates of total expenditures. However, if the estimate relates to the entire population, this file cannot be used to calculate the denominator, as only those persons with at least one outpatient event are represented on this data file. Therefore, the full year consolidated file must be used for person-level analyses that include both persons with and without hospital outpatient care.

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4.3 Variables with Missing Values

It is essential that the analyst examine all variables for the presence of negative values used to represent missing values. For continuous or discrete variables, where means or totals may be taken, it may be necessary to set minus values to values appropriate to the analytic needs. That is, the analyst should either impute a value or set the value to one that will be interpreted as missing by the software package used. For categorical and dichotomous variables, the analyst may want to consider whether to recode or impute a value for cases with negative values or whether to exclude or include such cases in the numerator and/or denominator when calculating proportions.

Methodologies used for the editing/imputation of expenditure variables (e.g., sources of payment, flat fee, and zero expenditures) are described in Section 2.5.6.

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4.4 Variance Estimation (VARSTR, VARPSU)

The MEPS is based on a complex sample design. To obtain estimates of variability (such as the standard error of sample estimates or corresponding confidence intervals) for MEPS estimates, analysts need to take into account the complex sample design of MEPS for both person-level and family-level analyses. Several methodologies have been developed for estimating standard errors for surveys with a complex sample design, including the Taylor-series linearization method, balanced repeated replication, and jackknife replication. Various software packages provide analysts with the capability of implementing these methodologies. MEPS analysts most commonly use the Taylor Series approach. However, the capability of employing the Balanced Repeated Replication (BRR) methodology is also provided if needed to develop variances for more complex estimators.

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4.4.1 Taylor-series Linearization Method

The variables needed to calculate appropriate standard errors based on the Taylor-series linearization method are included on this file as well as all other MEPS public use files. Software packages that permit the use of the Taylor-series linearization method include SUDAAN, Stata, SAS (version 8.2 and higher), and SPSS (version 12.0 and higher). For complete information on the capabilities of each package, analysts should refer to the corresponding software user documentation.

Using the Taylor-series linearization method, variance estimation strata and the variance estimation PSUs within these strata must be specified. The variables VARSTR and VARPSU on this MEPS data file serve to identify the sampling strata and primary sampling units required by the variance estimation programs. Specifying a “with replacement” design in one of the previously mentioned computer software packages will provide estimated standard errors appropriate for assessing the variability of MEPS survey estimates. It should be noted that the number of degrees of freedom associated with estimates of variability indicated by such a package may not appropriately reflect the number available. For variables of interest distributed throughout the country (and thus the MEPS sample PSUs), one can generally expect to have at least 100 degrees of freedom associated with the estimated standard errors for national estimates based on this MEPS database.

Prior to 2002, MEPS variance strata and PSUs were developed independently from year to year, and the last two characters of the strata and PSU variable names denoted the year. However, beginning with the 2002 Point-in-Time PUF, the variance strata and PSUs were developed to be compatible with all future PUFs until the NHIS design changed. Thus, when pooling data across years 2002 through the Panel 11 component of the 2007 files, the variance strata and PSU variables provided can be used without modification for variance estimation purposes for estimates covering multiple years of data. There were 203 variance estimation strata, each stratum with either two or three variance estimation PSUs.

From Panel 12 of the 2007 files, a new set of variance strata and PSUs were developed because of the introduction of a new NHIS design. There are 165 variance strata with either two or three variance estimation PSUs per stratum, starting from Panel 12. Therefore, there are a total of 368 (203+165) variance strata in the 2007 Full Year file as it consists of two panels that were selected under two independent NHIS sample designs. Since both MEPS panels in the Full Year files from 2008 through 2016 are based on the next NHIS design, there are only 165 variance strata. These variance strata (VARSTR values) have been numbered from 1001 to 1165 so that they can be readily distinguished from those developed under the former NHIS sample design in the event that data are pooled for several years.

As discussed, a complete change was made to the NHIS sample design in 2016, effectively changing the MEPS design beginning with calendar year 2017. Both Panels 22 and 23 reflect this new design. There were 117 variance strata originally formed under this new design intended for use until the next fully new NHIS design was implemented. They appear in the various MEPS data sets associated with 2017 as well as for the 2018 Point-in-Time PUF involving both Panels 22 and 23. However, it was later learned that the NHIS sample design was further modified in 2018, calling for a reconstruction of the previously established variance strata. Technically, this reconstruction would not be required until the MEPS 2019 PUFs were to be constructed. However, some analysts pool MEPS data across several years. In order to accommodate such pooling, the modification to the MEPS variance structure is being implemented initially for this 2018 FY PUF. Only a handful of variance strata have been affected with some pooling of previous strata being necessary. There are now 110 variance strata established for MEPS, compared to the 117 previously established.

In order to make the pooling of data across multiple years of MEPS more straightforward, the numbering system for the variance strata has changed. Those strata associated with the new design have four digit values with a “2” as the first digit. Those associated with the previous design have “1” as the first of four digits. If analyses call for pooling MEPS data across several years, in order to ensure that variance strata are identified appropriately for variance estimation purposes, one can proceed as follows:

  1. When pooling any year from 2002 or later, one can use the variance strata numbering as is.

  2. When pooling any year from 1996 to 2001 with any year from 2002 or later, use the H36 file.

  3. A new H36 file was constructed to allow pooling of 2007 and later years with 1996 to 2006.

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4.4.2 Balanced Repeated Replication (BRR) Method

BRR replicate weights are not provided on this MEPS PUF for the purposes of variance estimation. However, a file containing a BRR replication structure is made available so users can form replicate weights, if desired, from the final MEPS weight to compute variances of MEPS estimates using either BRR or Fay’s modified BRR (Fay 1989) methods. The replicate weights are useful to compute variances of complex non-linear estimators for which a Taylor linear form is not easy to derive and not available in commonly used software. For instance, it is not possible to calculate the variances of a median or the ratio of two medians using the Taylor linearization method. For these types of estimators, users may calculate a variance using BRR or Fay’s modified BRR methods. However, it should be noted that the replicate weights have been derived from the final weight through a shortcut approach. Specifically, the replicate weights are not computed starting with the base weight and all adjustments made in different stages of weighting are not applied independently in each replicate. Thus, the variances computed using this one-step BRR do not capture the effects of all weighting adjustments that would be captured in a set of fully developed BRR replicate weights. The Taylor Series approach does not fully capture the effects of the different weighting adjustments either.

The data set, HC-036BRR, contains the information necessary to construct the BRR replicates. It contains a set of 128 flags (BRR1—BRR128) in the form of half sample indicators, each of which is coded 0 or 1 to indicate whether the person should or should not be included in that particular replicate. These flags can be used in conjunction with the full-year weight to construct the BRR replicate weights. For analysis of MEPS data pooled across years, the BRR replicates can be formed in the same way using the HC-036 file. For more information about creating BRR replicates, users can refer to the documentation for the HC-036BRR pooled linkage file.

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5.0 Merging/Linking MEPS Data Files

Data from this file can be used alone or in conjunction with other files for different analytic purposes. This section summarizes various scenarios for merging/linking MEPS event files. Each MEPS panel can also be linked back to the previous year’s National Health Interview Survey public use data files. For information on obtaining MEPS/NHIS link files please see the data files section of the MEPS website.

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5.1 Linking to the Person-Level File

Merging characteristics of interest from other MEPS files (e.g., MEPS 2018 Full Year Consolidated File) expands the scope of potential estimates. For example, to estimate the total number of outpatient visits for persons with specific characteristics (e.g., age, race, sex, and education), population characteristics from a person-level file need to be merged onto the outpatient visit file. This procedure is illustrated below. The MEPS 2018 Appendix File, HC-206I, provides additional details on how to merge MEPS data files.

  1. Create data set PERSX by sorting the Full Year Consolidated file by the person identifier, DUPERSID. Keep only variables to be merged onto the outpatient visit file and DUPERSID.

  2. Create data set OPAT by sorting the outpatient visit file by person identifier, DUPERSID.

  3. Create final data set NEWOPAT by merging these two files by DUPERSID, keeping only records on the outpatient visit file.

The following is an example of SAS code that completes these steps:

PROC SORT DATA=HCXXX (KEEP=DUPERSID AGE31X AGE42X AGE53X SEX RACEV1X EDUCYR HIDEG) OUT=PERSX;
BY DUPERSID;
RUN;

PROC SORT DATA=OPAT;
BY DUPERSID;
RUN;

DATA NEWOPAT;
MERGE OPAT(IN=A) PERSX(IN=B);
BY DUPERSID;
IF A;
RUN;

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5.2 Linking to the Prescribed Medicines File

The prescribed medicines-event link (RXLK) file provides a link from the MEPS event files to the Prescribed Medicines Event File. When using the RXLK, data users/analysts should keep in mind that one outpatient event can link to more than one prescribed medicine record. Conversely, a prescribed medicine event may link to more than one outpatient event or different types of events. When this occurs, it is up to the data user/analyst to determine how the prescribed medicine expenditures should be allocated among those medical events. For detailed linking examples, including SAS code, data users/analysts should refer to the MEPS 2018 Appendix File, HC-206I.

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5.3 Linking to the Medical Conditions File

The condition-event link (CLNK) file provides a link from MEPS event files to the 2018 Medical Conditions File. When using the CLNK, data users/analysts should keep in mind that (1) conditions are household-reported, (2) there may be multiple conditions associated with an outpatient visit, and (3) a condition may link to more than one outpatient visit or any other type of visit. Users should also note that not all outpatient visits link to the medical conditions file.

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References

Chowdhury, S.R., Machlin, S.R., Gwet, K.L. Sample Designs of the Medical Expenditure Panel Survey Household Component, 1996—2006 and 2007—2016. Methodology Report #33. January 2019. Agency for Healthcare Research and Quality, Rockville, MD.

Cohen, S.B. (1998). Sample Design of the 1996 Medical Expenditure Panel Survey Medical Provider Component. Journal of Economic and Social Measurement. Vol 24, 25-53.

Cohen, S.B. (1996). The Redesign of the Medical Expenditure Panel Survey: A Component of the DHHS Survey Integration Plan. Proceedings of the COPAFS Seminar on Statistical Methodology in the Public Service.

Fay, R.E. (1989). Theory and Application of Replicate Weighting for Variance Calculations. Proceedings of the Survey Research Methods Sections, ASA, 212-217.

Monheit, A.C., Wilson, R., and Arnett, III, R.H. (Editors). Informing American Health Care Policy. (1999). Jossey-Bass Inc, San Francisco.

Shah, B.V., Barnwell, B.G., Bieler, G.S., Boyle, K.E., Folsom, R.E., Lavange, L., Wheeless, S.C., and Williams, R. (1996). Technical Manual: Statistical Methods and Algorithms Used in SUDAAN Release 7.0, Research Triangle Park, NC: Research Triangle Institute.

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D. Variable-Source Crosswalk

VARIABLE-SOURCE CROSSWALK

FOR MEPS HC-206F: 2018 OUTPATIENT DEPARTMENT VISITS

Survey Administration Variables

Variable Description Source
DUID Panel # + encrypted DU identifier Assigned in sampling
PID Person number Assigned in sampling
DUPERSID Person ID (DUID + PID) Assigned in sampling
EVNTIDX Event ID Assigned in sampling
EVENTRN Event Round number CAPI derived
PANEL Panel number Constructed
FFEEIDX Flat Fee ID CAPI derived
MPCDATA MPC data flag Constructed

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Outpatient Department Visit Variables

Variable Description Source
OPDATEYR Event date – year CAPI derived
OPDATEMM Event date – month CAPI derived
SEEDOC_M18 Did person talk to MD this visit OP10
DRSPLTY_M18 OPAT doctor’s specialty OP20
MEDPTYPE_M18 Type of medical person talked to on visit date OP30
VSTCTGRY Best category for care person received on visit date OP40
VSTRELCN_M18 This visit/phone call related to spec condition OP50
LABTEST_M18 This visit did person have lab tests OP80
SONOGRAM_M18 This visit did person have sonogram or ultrasound OP80
XRAYS_M18 This visit did person have x-rays OP80
MAMMOG_M18 This visit did person have a mammogram OP80
MRI_M18 This visit did person have an MRI/Catscan OP80
EKG_M18 This visit did person have an EKG, EEG or ECG OP80
RCVVAC_M18 This visit did person receive a vaccination OP80
SURGPROC Was surgical procedure performed on person this visit OP70
MEDPRESC Any medicine prescribed for person during visit OP90

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Flat Fee Variables

Variable Description Source
FFOPTYPE Flat fee bundle Constructed
FFBEF18 Total # of visits in FF before 2018 FF50
FFTOT19 Total # of visits in FF after 2018 FF60

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Imputed Total Expenditure Variables

Variable Description Source
OPXP18X Total expenditure for event (OPFXP18X+OPDXP18X) Constructed
OPTC18X Total charge for event (OPFTC18X+OPDTC18X) Constructed

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Imputed Facility Expenditure Variables

Variable Description Source
OPFSF18X Facility amount paid, self/family (Imputed) CP Section (Edited)
OPFMR18X Facility amount paid, Medicare (Imputed) CP Section (Edited)
OPFMD18X Facility amount paid, Medicaid (Imputed) CP Section (Edited)
OPFPV18X Facility amount paid, private insurance (Imputed) CP Section (Edited)
OPFVA18X Facility amount paid, Veterans/CHAMPVA (Imputed) CP Section (Edited)
OPFTR18X Facility amount paid, TRICARE (Imputed) CP Section (Edited)
OPFOF18X Facility amount paid, other federal (Imputed) CP Section (Edited)
OPFSL18X Facility amount paid, state & local government (Imputed) CP Section (Edited)
OPFWC18X Facility amount paid, workers’ compensation (Imputed) CP Section (Edited)
OPFOR18X Facility amount paid, other private insurance (Imputed) Constructed
OPFOU18X Facility amount paid, other public insurance (Imputed) Constructed
OPFOT18X Facility amount paid, other insurance (Imputed) CP Section (Edited)
OPFXP18X Facility sum payments OPFSF18X –OPFOT18X Constructed
OPFTC18X Total facility charge (Imputed) CP Section (Edited)

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Imputed Physician Expenditure Variables

Variable Description Source
OPDSF18X Doctor amount paid, self/family (Imputed) Constructed
OPDMR18X Doctor amount paid, Medicare (Imputed) Constructed
OPDMD18X Doctor amount paid, Medicaid (Imputed) Constructed
OPDPV18X Doctor amount paid, private insurance (Imputed) Constructed
OPDVA18X Doctor amount paid, Veterans/CHAMPVA (Imputed) Constructed
OPDTR18X Doctor amount paid, TRICARE (Imputed) Constructed
OPDOF18X Doctor amount paid, other federal (Imputed) Constructed
OPDSL18X Doctor amount paid, state & local government (Imputed) Constructed
OPDWC18X Doctor amount paid, workers’ compensation (Imputed) Constructed
OPDOR18X Doctor amount paid, other private insurance (Imputed) Constructed
OPDOU18X Doctor amount paid, other public insurance (Imputed) Constructed
OPDOT18X Doctor amount paid, other insurance (Imputed) Constructed
OPDXP18X Doctor sum payments OPDSF18X –OPDOT18X Constructed
OPDTC18X Total doctor charge (Imputed) Constructed
IMPFLAG Imputation status Constructed

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Weights Variables

Variable Description Source
PERWT18F Expenditure file person weight, 2018 Constructed
VARSTR Variance estimation stratum, 2018 Constructed
VARPSU Variance estimation PSU, 2018 Constructed

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