Kauffman Index for Entrepreneurial Activity - State Report 2005
The Kauffman Index of Entrepreneurial Activity is the first study to measure business start-up activity for the entire U.S. adult population at the individual owner level. The data are derived from the monthly Current Population Survey, a national population survey conducted by the U.S. Bureau of the Census and the Bureau of Labor Statistics.
Link
http://www.kauffman.org/pdf/kauffman_entrep_index_0905.pdf