Descriptive Statistics with CPS Outgoing Rotation Group Data

#1

Hi All,

I have two questions about using the CPS Outgoing Rotation Group data.

  1. I downloaded the Outgoing Rotation Group data by going to IPUMS-CPS and selected all of the person-level variables under “Outgoing Rotation Groups (Earner Study).” I dropped all observations whose month-in-sample value was not 4 or 8. However, when I try to replicate the union membership numbers on unionstat.com, which also uses the CPS-MORG data to run descriptive statistics by year, I find that the number of observations by year available through IPUMS is around 1/5 the number used to produce the numbers on unionstat.com. When I weight by earnwt/12, I also find the the number of union members in the U.S. by year is 20-50% lower than the estimates available through the BLS. Here is the Stata code I used:

gen annualwt = earnwt / 12
sum empl [iw=annualwt] if year== 1984
display r(sum)
sum unmem [iw=annualwt] if year== 1984
display r(sum)

Does anyone know why I can’t get accurate population estimates using the CPS-MORG data available through IPUMS-CPS with the above weighting?

  1. Which CPS weight should i use to find the % female workers by year in my CPS-MORG dataset?

Many thanks!

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#2

I’ll answer each question individually.

(1) It seems like that the tables available on www.unionstats.com are using only the basic monthly samples (and not the ASEC sample) for each year. When I pull all of the basic monthly samples (for a given year) and restrict the sample to only those in the Outgoing Rotation Group (MISH==4 | 8), I find observation counts close to what is reported in the online tables. I’ve also noticed that in your data extracts, you’ve only included ASEC samples. This will be a smaller sample, in terms of number of observations, compared to simply pooling all of the basic monthly samples. Additionally, once this detail is addressed, I calculate percentages that match the tables available online.

(2) To calculate the % female workers by year, I’d actually recommend not simply using your Outgoing Rotation Group dataset. The reason being is that this data is available for a much larger sample of the population and you’ll be able to calculate much more precise estimates if you use a larger sample. I’d suggest using the variable WORKLY, which is available in ASEC samples dating back to 1988. Then you can tabulate by SEX, while using the WTSUPP sample weight.

I hope this is helpful.

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#3

Thanks, Jeff. You’re completely right that I had incorrectly selected the ASEC samples rather than the basic monthly samples. Many thanks for spotting that.

Your point about the using a larger sample than the MORG sample is a good one. If I did want to look at % female in the MORG sample though, would I again weight by earnwt / 12 for the pooled annual sample?

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