U.S.-Mexico border arrests sharply down in 2008

Mexico-U.S. border arrests have fluctuated widely in the past 30-plus years, from 675,000 in 1976 to 1.7 million in the mid-1980s, down to a million in the late-’80s, back up to 1.6 million in 2000. In 2008, the Border Patrol caught 705,000 people trying to enter the U.S. illegally, down 44 percent from 2006. Officials say the construction of 526 miles of border fence, tougher prosecution, and a weak U.S. economy are all key reasons for the decline. But there's no way to tell, really.

According to the Congressional Research Service, the number of arrests is the most reliable measure of illegal crossings -- even though there is no way to count the number of people who actually do make it. The Pew Hispanic Center estimates that inflows of unauthorized immigrants averaged 800,000 per year from 2000-2004, but fell to 500,000 per year from 2005-2008. Pew also estimates that there are currently 11.9 million unauthorized immigrants in the U.S., about 4 percent of the population.

Some claim the number of illegal immigrants is down because the number of Border Patrol agents is up. In 1993, there were 4,000 agents. Fifteen years later -- after a 2006 mandate by President Bush to increase the force by 50 percent -- there are 18,000. But with fewer crossings, they may have nothing to do.