This document discusses how to merge household and individual files from two rounds of a survey, the India Human Development Survey (IHDS). It provides steps to link households and individuals surveyed in both rounds using a linking file, and describes how the merged files will contain cases surveyed in one or both rounds as well as new households and individuals. Key points are that reinterviewed households may have new or missing members, and variables from each round should be renamed before merging to preserve them separately.

1. INDIA HUMAN
DEVELOPMENT SURVEY
(IHDS)
TRAINING PROGRAM
MARCH 16, 2016
How to merge two rounds?

2. Merging Household Files

3. Relationship between IHDS-I
and IHDS-II households
IHDS-I sample
(N=41,554)
Replacement
households in
IHDS-II (N=2,134)
Split households
from round 1
(N=5,397)
Reinterview
Households
(N=34,621)
Attrition (N=6,911)
 Most important
concept in merging
two data files
1. Some households in
round 1 with no
match in round 2
and vice versa
2. Households in
round 1 match with
more than 1
household in round
2

4. Any questions?
 Who were chosen for reinterview?
 Recontact rate of 83%? What does it mean?
 How were replacement households chosen?
 What is a split household?

5. What is needed to merge
household files?
1. Round 1 household file – N=41,554
2. Round 2 household file – N=42,152
 (Why are there more cases in round 2?)
3. Linking file – N=42,152 – gives Round 1
identification codes for all Round 2
households that were reinterviewed, missing
linking codes for 2,134 households that are
new

6. Step 1 – Link round 2 data to
linking file to get round 1 ID
 use linkhh, clear
 sort STATEID DISTID PSUID HHID
HHSPLITID
 merge 1:1 STATEID DISTID PSUID HHID
HHSPLITID using round2HH
 sort STATEID DISTID PSUID HHID2005
HHSPLITID2005, gen(_mergeR2link)
 save round2HH_plus, replace

7. Step 2-Merge this Round 2+ file
with Round 1 file
 use round1HH
 rename HHID HHID2005
 rename HHSPLITID HHSPLITID2005
 sort STATEID DISTID PSUID HHID2005
HHSPLITID2005
 merge 1:m STATEID DISTID PSUID HHID2005
HHSPLITID2005 using round2HH_plus,
gen(_mergeR1R2)
 sort STATEID DISTID PSUID HHID HHSPLITID
 save mergedHHR1R2, replace

8. Cases in Merged file is superset
 Households surveyed in both rounds N=40,018
 Households surveyed in round 1 only (attrition)
N=6,911
 Households surveyd in round 2 only
(replacement) N=2,134
 Total N=49,063
 Keep only _mergeR1R2==3 for panel analysis
(N=40,018)

9. Merging Individual Files

10. Relationship between IHDS-I
and IHDS-II individuals
IHDS-I sample
(N=215,754)
New
individulas, new
HH (N=9,760)
New Ind in R1
HH (N=43,822)
Reinterview Ind
(N=150,995)
HH attrition
(N=29,299)
Ind. attrition in
interview hh
(N=35,464)
 Most important
concept in merging
two data files
1. Even reinterview
households have
new members
(births, marriages)
2. Even reinterview
households have
some members who
are no longer there
(deaths, marriages,
migration)

11. What is needed to merge
individual files?
1. Round 1 household file – N=215,754
2. Round 2 household file – N=204,568
 (Why are there more cases in round 2?)
3. Linking file – N=204,568 – gives Round 1
identification codes for all Round 2
households that were reinterviewed, missing
linking codes for 2,134 households that are
new

12. Step 1 – Link round 2 data to
linking file to get round 1 ID
 use linkind, clear
 sort STATEID DISTID PSUID HHID
HHSPLITID PERSONID
 merge 1:1 STATEID DISTID PSUID HHID
HHSPLITID PERONID using round2IND
 sort STATEID DISTID PSUID HHID2005
HHSPLITID2005, gen(_mergeR2link)
 save round2IND_plus, replace

13. Step 2-Merge this Round 2+ file
with Round 1 file
 use round1IND
 rename HHID HHID2005
 rename HHSPLITID HHSPLITID2005
 rename PERSONID PERSONID2005
 sort STATEID DISTID PSUID HHID2005
HHSPLITID2005 PERSONID2005
 merge 1:m STATEID DISTID PSUID HHID2005
HHSPLITID2005 PERSONID2005 using
round2IND_plus, gen(_mergeR1R2)
 sort STATEID DISTID PSUID HHID HHSPLITID
 save mergedINDR1R2, replace

14. Cases in Merged file is superset
 Individuals surveyed in both rounds N=150,988
 Individuals surveyed in round 1 only
(attrition/death/migration) N=64,766
 Individuals surveyd in round 2 only
(replacement/new) N=53,580
 Total N=269,334
 Keep only _mergeR1R2==3 for panel analysis
(N=150,988)

15. Evermarried woman file
linkage

16. Same process as individual file
linkage
 But only one thing to note, there was no ever
married woman file for 2004-5 so you will be
merging with the household file from 2004-5

17. Merging Caution

18. Merging overwrites variables
 So if you want to keep variables from round 1
and round 2 separate, before merging you may
want to rename all round 1 variables
 Typically we use the command
 Rename * x*
 Rename xSTATEID STATEID et. For merging
 So xr05 will be age in 20045 and r05 will be
age in 2011-12