The influx -- including Mexicans both with and without legal authorization to be in the United States -- is about 260,000 per year, according to the document released in Washington by the Migration Policy Institute.

The report compiled by economists with Mexico's central bank, said Mexican migration to the United States is less than the 280,000 who arrived annually over the last decade, and much lower than the 466,000 peak of 20 years ago.

The study, which said the figure could rise again in coming years, concluded that the dip in migration was likely due to the global financial crisis and tighter border restrictions following the September 11, 2001 terror attacks.

"The main conclusion we draw from our analysis is that net migration flows of Mexicans to the United States over the coming years are likely to increase as compared to what was observed during the recent global economic crisis, but that such flows are very unlikely to reach the levels registered during the 1990s," the report said.

There are about 12 million people of Mexican heritage living in the United States, making them by far the largest Hispanic group in the nation.

Hispanics number about 52 million in America, and are the country's largest minority group.