I am looking for information on the links between Counties and PUMAs for 2010. In particular I need the data on the population split for each county within each PUMA. This data exists for 1990 and 2000 on the IPUMS website. For example, the link below shows the relationship between PUMAs and standard census geographies (including counties) for the 2000 PUMAs. The file provides a detailed breakdown of how the population for each PUMA is allocated across counties (and other geographies). I cannot find a similar file for the 2010 PUMAs - that will be derived from the 2010 Census. Thanks in advance for your help!
You can get access to the equivalency files for 2010 PUMAs from the Census Bureau’s 2010 PUMA website. Click on the plus icon next to “Reference Information” to expand that section. You will see bold text that says 2010 PUMA Equivalency Files. I believe these are the files you are looking for.