Business Dynamics Statistics, BDS
"The new Business Dynamics Statistics are a product of the Center for Economic Studies of the U.S. Census Bureau. The annual series describes establishment-level business dynamics along dimensions absent from similar databases including firm age and firm size. The new data series provides researchers with a tool to gain insight into the dynamics of a changing economy...

The BDS series provides annual statistics for 1976-2005 by firm age and firm size. Annual files are also provided at the state level, for Standard Industrial Classification sectors and for the economy as a whole."