Arrests of illegal migrants trying to cross the southern U.S. border have plummeted to levels not seen since the early 1970s, according to tallies released by the Department of Homeland Security

The Border Patrol apprehended 327,577 illegal crossers along the U.S.-Mexico border in fiscal year 2011, numbers not seen since Richard Nixon was president, and a precipitous drop from the peak in 2000, when 1.6 million illegal immigrants were caught. More than 90% of the migrants apprehended on the southwest border are Mexican. Is this drop due to fewer illegal immigrants coming into the United States or is it due to the Obama administration putting pressure on the Border Patrol to apprehend fewer illegal immigrants?