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Linkage File for 2015 MEPS and 2013/2014 NHIS Public-use Files

1.0Overview

The MEPS-HC survey uses the NHIS as its sampling frame. Each year a new MEPS-HC panel is established drawing from the previous year’s NHIS sample. The MEPS-HC collects data through an overlapping panel design. In this design, two calendar years of information are collected from each household through in-person interviews, conducted over five rounds, with Round 3 spanning both calendar years.

For each panel, Rounds 1, 2, and part of Round 3 typically contain data from calendar year 1; the remaining part of Round 3, and Rounds 4 and 5 cover calendar year 2 for a panel. Therefore, MEPS full calendar year public-use data files contain data from the first year of a new panel combined with that of the second year of the previous panel. As illustrated below, for full calendar year 2015 estimates, Rounds 1, 2, and 3 of Panel 20 (which uses the 2014 NHIS as its sampling frame) are combined with Rounds 3, 4, and 5 of Panel 19 (which uses the 2013 NHIS as its sampling frame).

This image illustrates that 2015 data was collected in Rounds 3, 4, and 5 of Panel 19, and Rounds 1, 2, and 3 of Panel 20

Public-use files containing NHIS data for a given calendar year are available from NCHS.

Users who need to augment the MEPS data with information from NHIS can do so with the linkage file described in the following sections.

2.0Linkage File Description

The MEPS and NHIS linkage file, NHMEP15X.DAT, allows the data user to merge any of the person-level MEPS 2015 Full Year public use data files with the 2013 and 2014 NHIS person-level public-use data files (Person, Sample Adult, and Sample Child).

The NHIS person identifiers have been changed since 2004. Prior to 2004, one household equaled one "case" and unique person identifiers are Household Serial Number (HHX) and Person Number (PX). Since 2004, each family (FMX) is considered a separate case and unique person identifiers are Household Serial Number (HHX), Family Sequence Number (FMX), and Person Sequence Number (FPX).

The linkage file contains 35,427 person-level records and seven variables. In the linkage file, a record exists for each of the MEPS 2015 full-year persons. Each record contains the MEPS sample person ID (DUPERSID) and the corresponding NHIS sample person ID (HHX, FMX, and FPX). The linkage file can be linked to any of the person-level MEPS 2015 Full Year public use data files using the variable DUPERSID. The linkage file can be linked to the NHIS 2013 or 2014 person-level data files by HHX, FMX, FPX, and SRVY_YR.

When a MEPS sample person does not link to NHIS, HHX is set to 999999, FMX is set to 99, PX is set to 99, FPX is set to 99, SRVY_YR is set to 9999, and LINKFLAG is set to 0.

3.0Linkage File Record Counts

14,726 of the 16,578 Panel 19 persons link to the 2013 NHIS data, while 17,249 of the 18,849 Panel 20 persons link to the 2014 NHIS data. A total of 3,452 persons in the two panels do not link to either 2013 or 2014 NHIS data. These unlinked cases include newborns, newly in-scope persons as well as a small number of cases where the NHIS identified a household as responding but when fielded in MEPS it was determined to actually be a non‑responding household. The table below summarizes the linkages.

**Table 1 - Linkage File Record Counts**
	2013 NHIS PUF (n=104,520)	2014 NHIS PUF (n=112,053)	Not Linked to NHIS	Total
	Linked to NHIS		Not Linked to NHIS	Total
MEPS FY 2015 Panel 19 persons	14,726	0	1,852	16,578
MEPS FY 2015 Panel 20 persons	0	17,249	1,600	18,849
Total	31,975		3,452	35,427

4.0Linkage File Record Layout

Following is the record layout for the person-level MEPS/NHIS linkage file (NHMEP15X.DAT).
Variable	Column Position	Type	Label and value range
DUPERSID	1 - 8	Character	MEPS encrypted person ID (range=60001101-80571103)
HHX	9 - 14	Character	NHIS household serial number (range=000002 – 065122)
FMX	15 - 16	Character	NHIS family number (range=01-06)
FPX	17 - 18	Character	NHIS person number (range=01-18)
LINKFLAG	19 - 19	Numeric	Linkage status between MEPS and NHIS (1 or 0)
PANEL	20 - 21	Numeric	MEPS panel number (either 19 or 20)
SRVY_YR	22 - 25	Numeric	NHIS survey year (2013 or 2014)

Below is the input statement to convert the linkage file (NHMEP15X.DAT) to a SAS dataset.

DATA XX.NHMEP15X;
INFILE “C:\TEMP\MEPS\NHMEP15X.DAT”;
INPUT DUPERSID $1-8 HHX $9-14 FMX $15-16 FPX $17-18 LINKFLAG 19
PANEL 20-21 SRVY_YR 22-25;
RUN;

5.0Linking Instructions for SAS Users

The following is one way of adding NHIS person-level variables to the MEPS person-level file. Input files are: MEPS HC-174 (2015 Full-year Population Characteristics), 2013 NHIS person-level data file, 2014 NHIS person-level data file, and the linkage file NHMEP15X.DAT.

Create four SAS datasets as follows:
- Convert MEPS HC-174 (ASCII or SAS transport file) to a SAS dataset named FY2015 (n=35,427)
- Convert the linkage file NHMEP15X.DAT to a SAS dataset named NHMEP15X (n=35,427)
- Convert the 2014 NHIS Person file to a SAS dataset named NHIS2014 (n=112,053). Make sure the SAS dataset includes HHX, FMX, FPX, SRVY_YR, and other variables that are to be added to the MEPS full-year dataset.
- Convert the 2013 NHIS Person file to a SAS dataset named NHIS2013 (n=104,520). Make sure the SAS dataset includes HHX, FMX, FPX, SRVY_YR, and other variables that are to be added to the MEPS full-year dataset.
Sort FY2015 by DUPERSID. Concatenate NHIS2013 and NHIS2014 into one dataset named NHISALL (n=216,573). Sort NHISALL by HHX, FMX, FPX, and SRVY_YR.
Merge FY2015 (n=35,427) with NHMEP15X (n=35,427) by DUPERSID. Name the output dataset MEPS (n=35,427). Then sort MEPS by HHX, FMX, FPX, and SRVY_YR.
Merge MEPS (n=35,427) with NHISALL (n=216,573) by HHX, FMX, FPX, and SRVY_YR. Keep records only in MEPS (n=35,427). Name the output dataset MEPS15NH (n=35,427).

Below is a sample SAS program for adding NHIS variables to the MEPS dataset.

LIBNAME MEPS "C:\TEMP\MEPS"; /*MEPS 2015 Full-Year PUF*/
LIBNAME NHIS "C:\TEMP\NHIS"; /*NHIS 2013 and 2014 Person Files*/

PROC FORMAT;
VALUE AGE
.='.'
0-HIGH='>=0';
RUN;

DATA NHISALL;
SET NHIS.NHIS2013 (KEEP=HHX FMX FPX SRVY_YR AGE_P /*other NHIS variables*/)
NHIS.NHIS2014 (KEEP=HHX FMX FPX SRVY_YR AGE_P /*other NHIS variables*/);
RUN;

PROC SORT DATA=NHISALL;
BY HHX FMX FPX SRVY_YR;
RUN;

DATA MEPS;
MERGE MEPS.FY2015 MEPS.NHMEP15X (KEEP=DUPERSID HHX FMX FPX SRVY_YR LINKFLAG);
BY DUPERSID;
RUN;

PROC SORT DATA=MEPS;
BY HHX FMX FPX SRVY_YR;
RUN;

DATA MEPS.MEPS15NH;
MERGE MEPS (IN=A) NHISALL;
BY HHX FMX FPX SRVY_YR;
IF A;
RUN;

TITLE1 "MEPS 2015 FY data with NHIS variables";
PROC FREQ DATA=MEPS.MEPS15NH;
TABLES LINKFLAG*SRVY_YR*AGE_P/LIST MISSING;
FORMAT AGE_P AGE.;
RUN;

6.0Sample Stata Code for Adding NHIS Variables to the MEPS Dataset

clear

log using stata15.log, replace

use c:\temp\meps\fy2015
sort dupersid
save fy2015, replace

use c:\temp\nhis\nhis2013
append using c:\temp\nhis\nhis2014
save nhisall, replace

use nhisall
sort hhx fmx fpx srvy_yr
save nhisall, replace

use c:\temp\meps\nhmep15x
sort dupersid
save link, replace

use fy2015
merge dupersid using link
drop _merge
save meps, replace

use meps
sort hhx fmx fpx srvy_yr
save meps, replace

use meps
merge hhx fmx fpx srvy_yr using nhisall
keep if _merge==3 | _merge==1
keep dupersid hhx fmx fpx srvy_yr linkflag /*plus nhis variables wanted to add*/
save c:\temp\meps\meps15nh, replace

describe
tab1 linkflag srvy_yr

7.0Further Information

For any questions regarding the linkage file, please contact May Chu at 301-427-1653 or by email at May.Chu@ahrq.hhs.gov. MEPS public use data files can be downloaded free of charge from the MEPS website at http://www.meps.ahrq.gov. NHIS public use data files can be obtained by contacting NCHS by telephone (301-458-4636) or through their website, http://www.cdc.gov/nchs.