Public Use Microdata Area

Public Use Micro Data Sample Areas (PUMAs)

Public Use Micro Data Sample Areas, or PUMAs, is a division of US States into census area which each contain around 100.000 people. All such areas are non overlapping and partition a State. There are a total of 2,071 PUMAs. The State governments drew the PUMA boundaries for the 2000 Census, to allow reporting of detailed data for all areas. For example the American Community Survey publishes detailed data every year, but due to their sampling procedure only publishes data for census area that have more than 65.000 People. PUMAs allows the publishing of census data for most sub-state areas. Take West Virginia, for example, which has 55 counties. Only seven of these 55 counties are large enough to receive estimates from the 2006 ACS. However, because West Virginia is partitioned into 12 PUMAs, each of these areas will receive 2006 ACS estimates.

reference http://www.census.gov/acs/www/Downloads/Handbook2006.pdf