The number of illegal immigrants entering the United States has slowed significantly the past few years, falling below the number of those entering the country legally, according to the report by the Pew Hispanic Center, a Washington think tank.
The report estimates there were 11.9 million illegal immigrants in the U.S. as of March. That would be a decline of 500,000 from the center's estimate a year ago. However, the change was not statistically significant because of the large margins of error.
The Pew study does not address why the decrease occurred, but other researchers cite the nation's struggling economy and stepped up enforcement of immigration laws.
