Summary on ACS Annual Ancestry Variables (Tract level and above)

Notes from ACS ancestry variables Source: On p.48 of this PDF are definitions of ACS ancestry variables :

• Ancestry is required to enforce provisions under the Civil Rights Act.
• The Detailed Tables (B04001-B04007) contain estimates of over 100 different ancestry groups.
• People Reporting Ancestry:* Includes all people who reported each ancestry, regardless of whether it was their first or second ancestry, or part of a single or multiple response.
• The question on ancestry has been asked on the 1980, 1990, and 2000 census and in American Community Survey since 1996... "ACS data are comparable to Census 2000, as long as some caution is used..."

Notes on census redistricting data, PL94-171 Source Berkeley Law redictricting group:

• Census blocks are the building blocs for the creation of districts.

ACS data versus redictricting data:

• sample versus universe
• range of time versus snapshot in time

ACS 2011 is from responses between 2006 and 2010. Useful variable is Citizen Voting Age Population or CVAP.