U.S. Census Bureau,
"Population, Population change and estimated components of population change: April 1, 2000 to July 1, 2006.
Release data: December 22, 2006;
http://www.census.gov/popest/national/files/NST_EST2006_ALLDATA.csv
For more information:
http://www.census.gov/popest/datasets.html
referenced on dataset section Notes (#2)
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