The Census Bureau has a snazzy new two-minute video explaining the apportionment of House seats to the states based on the results of the decennial census. The video, The Amazing Apportionment Machine, is featured in the 9 December 2010 Washington Post article Census wisely explains reapportionment.
The Census Bureau also offers a 2010 Congressional Apportionment Countdown Clock widget for embedding in your website. From the Census site: "As mandated by the US Constitution, this data must be delivered to the President of the United States by the US Census Bureau on or before December 31, 2010."
The bureau explains the history and process on their Congressional Apportionment page.
The Clerk of the House website also details the history of apportionment and offers a chart of historical apportionment by state listing the number of representatives apportioned to each state from the first federal census to the present.
On 14 December 2010, Census is scheduled to release the data from the first 5-year American Community Survey (ACS) report. This is not data used for reapportionment. Census Director Robert Groves explains in his blog post A Data Filled Fall:
In early December, we will release the 2005-2009 ACS 5-year estimates...These are NOT 2010 Census results, but are based on survey data collected between January 2005 and December 2009. We will release these estimates for the smallest geographic areas including census tracts (units of about 4,000 people) and even smaller, block groups.
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