I am using IPUMS-ACS and need to know what these values : -9999 and 666000 mean in incwage variable.
Also, in the birthplace variable, I need to identify those born in the US, but I only find US states and not the whole country as birthplace. Is there any way to identify those born in the usa without grouping US states?
As noted here, INCWAGE is top coded. For the ACS from 2003 onward, it is at the 99.5th percentile in state. Therefore, 660000 is a top code, specifically, it looks like it is the top code for CT in 2007. You can find this information for all years here. Additionally, income amounts which can have negative values are bottom-coded, which would be why you observe -9999.
Regarding BPL, unfortunately, you will have to group the state together, however this should be relatively simple. Codes for the United States (including Native American, no state given, and US outlying areas/territories) are from 001 - 120. Anything else up to 900 would be Non-US born.
Thanks so much for your response. It is very useful