Published: Feb 01, 2011 6:44 PM EST
Updated: Feb 01, 2011 3:44 PM EST

WASHINGTON (AP) - Could the flow of illegal immigrants into the U.S. be ready to increase again? The authors of a new study aren't sure.

The study finds that after declining during the recession, the number of illegal immigrants living in the United States was virtually unchanged last year from a year earlier.

In 2009, the level of illegal immigration had declined for the first time in two decades. It was due in part to a sour economy and to stepped-up border enforcement.

The study from the nonpartisan Pew Hispanic Center also finds that the number of illegal immigrants in the U.S. labor force was unchanged last year at 8 million. that represents about 5 percent of workers in the country. It hit a peak of 8.4 million in 2007.

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