For COUNTRY, 50200 indicates “Korea” and 50220 indicates “South Korea”. Thus, does it mean 50200 is actually North Korea?
This is a great question – 50200 does not correspond to North Korea exclusively; it captures people who reported “Korea” without further specification. The original ASEC data in these years assigns responses of “Korea” and “South Korea” to separate codes; the original codebooks (see 2005 ASEC codebook for reference) do not include “North Korea” as a code for this variable.
IPUMS CPS uses a strategy called composite coding to simplify the process for aggregating codes; this is helpful when working with highly detailed responses that many users will choose to combine into a single category, or when combining multiple samples that may offer different levels of detail. Under composite coding, the first digit(s) of the codes indicate broadly comparable categories, while the trailing digits are used to identify more detailed subgroups. For example, in the COUNTRY variable, the code for all Asian countries begin with a 5; all East Asian countries have codes beginning with a 50 while Southeast Asian countries have codes that begin with 51. Under this approach, users may coarsen the codes as seems appropriate for their analysis or the data availability (e.g., group all East Asian countries together by collapsing the 50000-51800 codes into a single category). In the case of the Korea and South Korea responses, you might combine the 50200 and 50220 categories into a broader “Korea” group.
The codes used in the IPUMS CPS COUNTRY variable are derived from the IPUMS USA birthplace variable, which does include North Korea in some years (note you will need to click on the “detailed codes” radio button at the top of the codes tab to see this). We use the IPUMS USA BPL codes both to facilitate comparability between the IPUMS USA and IPUMS CPS data collections, and because nesting the appropriate codes within broader comparable categories can be quite involved (particularly in cases like BPL and COUNTRY).