Question about county data for 2012 ACS

In 2012 ACS, why are there “0” values for some counties, such as Los Angeles (STATEFIP=6, COUNTY=370) ? Thanks a lot!

As explained in the COUNTY variable description in order for counties to be identified in modern samples they had to meet one of the two criteria:

  1. County was coterminous with a single identifiable SEA, county group, or PUMA; or
  2. County contained multiple identifiable SEAs, county groups, or PUMAs, none of which extended into other counties.

Because the 2012 ACS was the first PUMS file to use new PUMA codes and definitions based on the 2010 Decennial Census some counties that were previously identifiable are not identifiable in the 2012 sample. Likewise, some counties that previously were not identifiable using the 2000 Decennial Census based PUMA codes and definitions are now identifiable in the 2012 ACS sample.

As to Los Angeles county, though it is not currently identified in the 2012 ACS sample on IPUMS-USA it is actually identifiable using the STATEFIP==06 AND PUMA==3701-3769. IPUMS-USA will release an updated version of the COUNTY variable with Los Angeles identified by the end of the summer if not sooner.

I hope this helps.