The 2011 GEM report is based on a survey of 140, 000 adults in 54 economies, including 6, 000 just in the U.S. Researchers looked at responses from a random sampling of participants, as well as population data for each of the countries represented, to draw conclusions about entrepreneurial activity in those nations.

WSJ: Rise in Start-Ups Draws Doubters

If it used these sampling methods, the Census Bureau says, there is a 90% chance that its estimate of America's population would be within 0.1% of the true number.

ECONOMIST: Statistics