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ID Variables in the March CPS

The March CPS has two person ID variables. Which one should a user interested in merging husbands with wives or parents with children use?

The relevant variables from the March 1998 CPS are described below:

Variable Definition Size Begin Range
PH-SEQ Household seq number 2 5 00001:99999
PPPOS Trailer portion of unique household
ID.
2 7 41:79
A-LINENO Line number 2 9 01:39
A-PARENT Parent’s line number 2 11 00:39
A-SPOUSE Spouse’s line number 2 18 00:39
A-EXPRRP Expanded relationship code
01 Reference person with relatives
02 Reference person without relatives
03 Husband
04 Wife
05 Own child
07 Grandchild
08 Parent
09 Brother/sister
10 Other relative
11 Foster child
12 Nonrelative with relatives
13 Parnter/roommate
14 Nonrelative without relatives
2 13 01:14
A-SEX Sex
1 Male
2 Female
1 20 1:2
A-MARITL Martial status
1 Married – civilian spouse present
2 Married – AF spouse present
3 Married – Spouse absent
4 Widowed
5 Divorced
6 Separated
7 Never married
1 17 1:7

The following are selected person records from the March 1998 CPS. It is clear that parent’s line number (A-PARENT) and spouse’s line number (A-SPOUSE) are referring to line number (A-LINENO) rather than the trailer portion of the unique household ID (PPPOS).

PH-SEQ PPPOS A-LINENO A-PARENT A-SPOUSE A-EXPRRP A-SEX A-MARITL
63569 41 01 00 00 02 2 7
24026 41 01 00 00 02 2 7
24025 41 01 00 02 01 1 1
24025 42 02 00 01 04 2 1
24024 41 01 00 02 01 1 1
24024 42 02 00 01 04 2 1
24023 41 01 00 02 01 1 1
24023 42 02 00 01 04 2 1
24023 43 03 01 00 05 2 7
24023 44 04 01 00 05 2 7
24021 41 01 00 00 02 2 5
24020 41 01 00 02 01 1 1
24020 42 02 00 01 04 2 1

For the most part, the difference between A-LINENO and PPPOS is "40." However, one should not create a new variable:

PERSONID = PPPOS – 40;

This is because, on occasion, the difference between A-LINENO and PPPOS is not "40." See the following records from these data:

PH-SEQ PPPOS A-LINENO A-PARENT A-SPOUSE A-EXPRRP A-SEX A-MARITL
00232 41 01 00 02 01 1 1
00232 42 02 00 01 04 2 1
00232 43 03 01 00 05 1 7
00232 44 04 01 00 05 2 7
00232 45 06 00 05 10 2 1
00232 46 05 00 06 10 1 1
00232 47 07 06 00 10 2 7
00232 48 08 06 00 10 1 7
02086 41 02 00 01 01 2 1
02086 42 01 00 02 03 1 1
07676 41 01 03 00 01 1 7
07676 42 03 00 02 08 2 1
07676 43 02 00 03 08 1 1

An explanation for the difference between PPPOS and A-LINENO is provided by Greg Weyland of the Census Bureau:

In many cases it is true that a person's line number and their PPPOS value are identical, but they are not always so. This is because these variables come from different sources and have somewhat different uses. The PPPOS variable is only found on the March files. It is a strict count of the number of person records within a household and is assigned in an order consistent with a certain predetermined structure of the household. A-LINENO, on the other hand, is a variable that appears on all CPS files. It is a number that is consistent with the household roster of individuals provided at the time of interview. It does not change throughout a household's time in the CPS sample.

For example, a household may have 5 individuals listed on the roster at the time of the first interview. These individuals would have line numbers of 1-5 assigned to them. If say line number 3 moves out after the second month interview, Line numbers 4 and 5 retain their values and the household will appear on CPS files without a line number 3. For the same household, if March occurred during the first month interview, PPPOS 1-5 would be used. If, however, the March interview occurred in the third month interview, only PPPOS values of 1-4 would be found for the household. Moves into and out of the household can also cause the PPPOS values to be assigned in a manner that is not consistent with the order of line numbers in a household.