PHOENIX (Reuters) - The number of illegal immigrants in the United States leveled off at around 11 million last year, ending a two-year slide since the start of the recession, according to a study released on Tuesday.
The study by the Pew Hispanic Center noted 11.2 million illegal immigrants living and working in the shadows in the United States in March 2010, virtually unchanged from a year earlier.
The report, which drew on U.S. Census Bureau data, noted the number of illegal immigrants in the workforce remained steady at around 8 million.
The leveling off last year followed a two-year slide in the population to 11.1 million in 2009 from a peak of 12 million in 2007, at the start of the U.S. recession.
"What we have seen in the past is that the flow of unauthorized immigrants, particularly from Mexico, has been very closely tied to the state of the U.S. economy," senior demographer Jeffrey S. Passel told Reuters.
"We've seen large drops in the inflows when the U.S. went into a recession, and large increases when the U.S. economy was booming," he added.
The issue of what to do with the shadow population divides Americans.
President Barack Obama backs comprehensive immigration reform, tightening enforcement while giving millions of illegal immigrants a shot at legal status, while Republicans generally favor an enforcement-only approach.
Gridlock in Washington has led Republican legislators in a growing number of states to push measures curbing illegal immigration and challenging birthright citizenship for the immigrants' U.S.-born children.
The study found the decline in the number of illegal immigrants has been especially marked in Colorado, Florida, New York and Virginia -- which had previously noted growth in their unauthorized population -- as well as in Arizona, Nevada and Utah.
Passel said factors including a struggling local economy, together with local initiatives to crack down on illegal immigrants, likely contributed to the decline.
"We can point to the economy as perhaps the principal factor ... (although) Arizona and Virginia also passed restrictive legislation to limit undocumented immigration," he said.
Reporting by Tim Gaynor; Editing by Jerry Norton