U.S. entrepreneurial activity fell from 12.4 percent of the total workforce in 2005 to 9.6 percent in 2007, according to a joint study by Babson and Baruch Colleges.

Despite the decline, the nation's rate of entrepreneurship was 50 percent higher than in other comparable countries, the study reported.

While more businesses were founded in the United States than in other countries last year, many aren't expected to grow or create new jobs over the next five years.

Opportunity remained the biggest motivator for starting a business, though the percentage of entrepreneurs who launched a start-up out of necessity rose from 12.1 percent in 2005 to 15.6 percent in 2007, the study found.

Minorities continued to show higher rates of entrepreneurship than within the general population. Researchers said employment discrimination could be a contributing factor. The study found that more than 70 percent of African Americans and more than 72 of Mexican Americans started businesses after feeling they were rejected for a job because of their ethnicity.