Arrests of people trying to sneak into the U.S. from Mexico have plunged to the lowest level in four decades, the latest sign that illegal immigration is on the retreat even as legislatures, Congress and presidential candidates hotly debate the issue.
Behind the historic drop is a steep decline in the birthrate in Mexico and greater opportunities there relative to the weak U.S. economy. Stepped-up U.S. patrols along the border make it both riskier and more expensive for Mexicans to attempt to enter the country.
Government crackdowns on U.S. employers who hire illegal workers also have discouraged immigrants. The Supreme Court agreed Monday to decide whether an Arizona statute targeting illegal immigrants interferes with U.S. law.
The decline in Mexican immigrants is being felt as far away as farms in Washington and Michigan, which weathered labor shortages during the recent apple harvest.
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The U.S. arrested 340,252 migrants along the Mexico-U.S. border in the fiscal year that ended Sept. 30—down 24% from the year before and the lowest level in 39 years, according to U.S. Customs and Border Protection, a unit of the Department of Homeland Security.
In the previous fiscal year, agents apprehended 447,731 illegal crossers in the Southwest, compared with 1.6 million in 2000, the peak year. The last time the border was this quiet was 1972, when agents caught 321,326 people.
"We have reached the end of an era," said Dowell Myers, a demographer at the University of Southern California. "Even if immigration increases some after this recession, it won't rebound back to levels we saw in the early 2000s."
Rafael Garcia, a 40-year-old undocumented immigrant in Washington State, said he would discourage Mexican friends from attempting to enter the U.S. illegally, even though he has worked in vineyards, apple orchards and dairy farms in the country for two decades.
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"You have to be really desperate to come here now," said Mr. Garcia, who is married with three U.S.-born daughters. "It's so hard to get across, and then you have all these states passing laws to get rid of you."
The dramatic decrease in border arrests—which the U.S. considers a key gauge of how many people try to enter illegally—is supported by figures that show a shrinking number of illegal immigrants already in the country.
In 2010, that undocumented population was estimated at 11 million by the independent Pew Hispanic Center, down 8% from its peak of 12 million in 2007.
Mexicans constitute about 60% of undocumented U.S. immigrants. "Current flows are as low as we have ever seen them," said Jeffrey Passel, a senior researcher at the Pew center. "More unauthorized Mexicans have been leaving than coming."
At 150,000 last year, Mexican immigration to the U.S. was one-fifth of what it was in 2000, when 750,000 Mexicans flocked to the U.S., the majority of them illegally. All told, net immigration from Mexico is "essentially zero," said Mr. Passel.
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Nearly 21,500 agents, about twice as many as in 2004, guard the Southwestern border. They are backed by hundreds of miles of fencing and high-tech surveillance, including thermal imaging and unmanned aerial systems.
Mexican drug cartels also may play a role in discouraging people. The cartels often ply the same routes to the U.S. that undocumented immigrants use, making those paths violent and dangerous. Some crossers have been forced to serve as drug carriers for cartels.
Some demographers say more undocumented Mexicans may be leaving the U.S. than arriving as a downturn in construction, hospitality and other industries makes low-skill jobs scarce. Thousands of illegal immigrants have lost their jobs after the U.S. has audited company payrolls to find undocumented workers.
"No one knows better than the migrants themselves about the state of the U.S. economy. They hear that their cousin, uncle and friends are without work," said Primitivo Rodriguez, a Mexican migration expert who formerly worked for the Mexican Human Rights Commission.
Back in Mexico, families have shrunk, providing less incentive for young people to leave. In 1970, each Mexican woman bore an average of 6.8 children. By 1990, that number was 3.4. Today, the birthrate is at replacement level, about 2.1.
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That "enormous demographic shift," coupled with a better economic climate in Mexico, is helping curb emigration, said Gordon Hanson, an international economist at the University of California, San Diego.
To be sure, annual immigration to the U.S. from its neighbor has climbed and receded before. It dropped by one-third after the terrorist attacks of Sept. 11, 2001. The annual influx of Mexicans averaged 550,000 between 2003 and 2006, according to Pew. It has since tumbled.
Still, illegal immigration remains a contentious political issue. More than one million people have been deported since President Barack Obama took office in 2009. Deportations hit a record 397,000 in the fiscal year ended Sept. 30. The president favors putting undocumented workers on the path to legalization. But as the 2012 election approaches, no immigration bill is expected to come before the House and Senate.
The impasse has propelled several states, such as Arizona, Alabama and Georgia, to pass laws to curb illegal immigration. Supporters say undocumented workers are taking jobs from Americans at a time of high unemployment and burdening cash-strapped public governments.
Except for former House Speaker Newt Gingrich, who said those in the U.S. more than 20 years should be able to earn legal status, top Republican presidential candidates oppose letting illegal immigrants remain in the U.S.
Write to Miriam Jordan at email@example.com