Immigrants make up 13% of the U.S. population but own 18% of the country's small businesses, according to a report from the Fiscal Policy Institute.

Immigrants head up 30% of the new small businesses created in the USA over the past two decades, according to the report released today by the New York-based think-tank.

READ: The full report

The analysis comes as Congress debates several proposals to open the country's immigration system to more entrepreneurs.

A start-up company in California has even proposed to anchor a ship off the California coast to house foreign entrepreneurs who cannot secure hard-to-get U.S. visas.

The Fiscal Policy Institute report found that owners of small businesses – described as employing fewer than 100 people – reached 900,000 in 2010, a 67% increase from 1990.

Those businesses employed 4.7 million people and generated an estimated $776 billion in receipts in 2007, the most recent year that data were available.

"Immigrants are playing a particularly important role in the kinds of businesses that bring people into downtown areas and help enliven neighborhoods," says David Dyssegaard Kallick, director of the institute's Immigration Research Initiative and author of the report.

The study finds that foreign-born business owners account for 65% of taxi and limousine services, 54% of dry cleaning and laundry services, 53% of gasoline stations and 49% of grocery stores.

There are some surprises. For example, even though immigrants make up a large share of workers in the construction sector, only 13% of real estate businesses are owned by immigrants.

Mexicans make up the largest share of foreign small-business owners, claiming 12% of businesses. Indians account for 7% and Koreans make up 6%. Cubans, Chinese and Vietnamese each account for 4% of foreign-owned small businesses.