Roughly 147 million people, or 10 percent of the adult population in 29 countries reviewed in the study, participated in some kind of entrepreneurial activity. Of that total number, 92 million, or 62 percent, resided in three countries--the U.S., Brazil, and India.

Although the high rankings for the U.S. and Brazil may not have been too surprising, India's third-place spot was somewhat unexpected. The country has a plentiful supply of human capital and is competitive in such industries as software and IT, but it suffers from an inadequate infrastructure, high equipment costs, restricted access to foreign resources, and limited domestic demand, the study noted.

At the same time, the study also ranked Australia, New Zealand, and Mexico as the most active countries entrepreneur-wise in 2001.