The net flow of illegal immigrants to the United States has trailed off to around zero since the recession began to bite in December 2007, according to a research study.
The report by the Migration Policy Institute think tank released on Wednesday found the US illegal immigrant population remained steady at around 12 million last year as the economy shed around 2.6 million jobs.
"When the economic climate in the United States changes dramatically for a period of time, the first flow to respond is that of unauthorized immigrants," Institute president Demetrios Papademetriou said in a telephone interview.
"Net illegal migration has been at a standstill, inflows and outflows come out at zero," he added.
Immigration, particularly what to do with some 12 million illegal immigrants living and working in the shadows, is an emotional topic in the United States, where Barack Obama becomes the new president on Jan. 20.
Recent government efforts to curb the flow have sought to ramp up security on the porous U.S.-Mexico border, where most illegal migrants cross, and in stepping up workplace immigration raids and deportations.
The report found the decline came largely as a result of fewer unauthorized migrants attempting the journey from Mexico and Central America.
"All sorts of things come in to play. The most important of which is the reduced economic opportunities in the United States, (although) border enforcement also plays a role," said Papademetriou.
LEGAL IMMIGRATION SLOWS
Around 38 million foreign-born people live in the United States, according to recent government figures.
For much of the past decade, more than one million immigrants including authorized workers and refugees have entered the country legally, and around half a million a year by illegal means.
The study found that the number of permanent legal immigrants moving to the United States had slowed since 2007, although it said the overall flow was less susceptible to the current economic downturn, the worst since the Great Depression of the 1930s.
The majority of legal immigrants are in fact permanent residents already in the United States adjusting their status, the report said, or workers awaiting visas, many of them snarled in an administrative backlog.
"Pent-up demand for employment sponsored visas means that actual lower admissions in these categories are not anticipated in the immediate future," it added.
The relatively smaller number of refugees accepted into the United States -- fewer than 75,000 last year -- is determined primarily by world events and government policy, and is not expected to be affected significantly by the economic cycle.
"While budget allocations for the refugee resettlement program can be susceptible to budget cuts that often occur during economic downturns, overall one should expect foreign wars, other international political upheavals ... to be much more important than U.S. economic conditions in determining refugee flows." it said.
(Reporting by Tim Gaynor; Editing by Vicki Allen)