Hi.
If I understand correctly, the first 6 digits of the IPUMS variable CPSIDP is the year and month that a particular household was first in the CPS. And if I was to create a calendar date based on that year and month and add (mish-1) if mish <=4 or (mish+7) if mish>4, then I should get the same date provided by the variables month and year.
For the most part, this is what happens. Here is an example when it is correct:
|year |month |mish|cpsidp | surdate |caldate|
|2000|january|eight|19981000005401|2000m1 |2000m1|
Where caldate is the calendar date based on the year and month vaariable and surdate was calculated as the date of the first 6 digits of cpsidp +mish-7 (see above). Notice surdate is the same as caldate in this example.
And here is an example of when there is an error:
|year |month|mish|cpsidp |surdate|caldate |
|2021|july |five |20210706771601|2022m7|2021m7|
Notice how surdate (calculated as the date from cpsidp + mish +7) is one year ahead of caldate. Mish in this latter case should be one and not 5.
In an extract consisting of all Basic Monthly CPS surveys from January of 2000 through July of 2021, I noticed that over 6 percent of the observations were subject to this errror. Here is the breakdown:
zz | Freq. Percent Cum.
------------±----------------------------------
0 | 31,770,795 93.84 93.84
1 | 160,873 0.48 94.32
2 | 110,930 0.33 94.64
3 | 90,260 0.27 94.91
12 | 1,529,077 4.52 99.43
13 | 121,941 0.36 99.79
14 | 49,177 0.15 99.93
15 | 23,082 0.07 100.00
------------±----------------------------------
Total | 33,856,135 100.00
zz is the difference between surdate and caldate.
My question, in order to fix this discrepancy, is what was miscoded? MISH or CPSIDP?
Thank you.
–Stuart M. Glosser
Professor of Economics (Emeritus)
University of Wisconsin at Whitewater