As the July 2010 Census publication, “Strength in Numbers - Your Guide to Census 2010 Redistricting Data From the U.S. Census Bureau”, relates :
The decennial census has
played a crucial role in the apportionment of the Congress for more than two
centuries. But it is only in the last 35 years that the Census Bureau has
played a major role in the redistricting process.
U.S. Supreme Court
decisions handed down during the 1960s clarified the Constitution’s intention
to provide equality of representation for all Americans. In 1964, the Wesberry
v. Sanders decision held that, “as nearly as is practicable one person’s
vote in a congressional election is to be worth as much as another’s.” That
same year, in Reynolds v. Sims, the Court ruled that state legislative
districts must be “as nearly of equal population as is practicable.”
Both U.S. congressional districts and state legislative districts must be drawn so that their residents have a fair and equal share in the way they are governed. These Supreme Court decisions increased the states’ need for geographically detailed census information in the redistricting process. The urgency of the states’ need for these data led the Congress to pass Public Law (P.L.) 94-171 in December 1975.
Distinct programs carried out by the Census Bureau. Data is gathered by different means for different purposes :
Decennial Census determines the nation's official population count and Is constitutionally required for the apportionment of the seats in the House of representatives. It is also used by state legislatures to redraw their own voting districts.
TIGER/Line® Shapefile Products (Topologically Integrated Geographic Encoding and Referencing system ) are like a huge digital map of the U.S. Using the TIGER/Line® shapefiles (the public version of the TIGER database) and appropriate software, users can rapidly determine the impact on the demographic makeup of a district when you move a boundary. This analysis can be quickly performed at all levels, from city blocks to congressional districts.
The American Community Survey ( ACS) is the successor to the former census "long form" that historically produced demographic, housing and socio-economic data for the nation as part of the once-a-decade census. For the ACS , housing units are sampled annually in all counties in the 50 states and the District of Columbia and to all 78 municipios in Puerto Rico. (Long-form was approx. a 16.5% sample. American Community Survey is based on approx. 12.5% sample.) The American Community Survey is conducted under the authority of Title 13, United States Code, Sections 141 and 193, and response is mandatory.
Population Estimates are done annually to give a total population count and a description by a few demographic characteristics. They serve as the official counts in between years without a census. The population estimates use a variety of administrative records data to measure the population change including data on births, deaths, migration, and housing units from the base population from the Decennial Census enumeration.
Significant release dates for 2010 Census related data and information :
On or before December 31, 2010 - official counts are to be reported to the President .
In December 2010 - TIGER/Line® shapefiles will be available with all of the 2010 Census geographic codes shortly before the 2010 Census summary file data become available.
Sept. 16, 2010 - 2009 Current Population Survey Income, poverty and health insurance estimates.
Sept. 28, 2010 - one-year estimates from 2009 American Community Survey.
November / December 2011 - set of five-year ACS estimates covering 2005-2009 , characteristics of small population areas (below 20,000).
January 2011 - the three-year estimates from the 2007-2009 American Community Survey.
February – March 2011 - release of Redistricting Data Files to state legislatures. Within a few days content will be posted to the Census “American Factfinder” website.
According to Gerald O’Donald from the Census Bureau speaking at the July 2010 AALL Conference (American Association of Law Libraries), not much of the 2010 Census data will be made available in print, less than was provided by GPO in 2000. He also indicated that the primary online public access tool, “American Factfinder”, will be re-designed in January 2011 and have a new look.