By JAMES PINKERTON

Arrests of illegal immigrants have plummeted in parts of Texas and along most of the Southwest border, where government agents in one Arizona sector have detained 78 percent fewer border crossers than last year.

So far this fiscal year, apprehensions are down in all but two of the nine U.S. Border Patrol sectors on the U.S.-Mexico border, officials confirmed. During the first 11 months of the fiscal year starting October 2007, roughly 660,000 illegal immigrants were detained along the Southwest border, an 18.4 percent drop from the same period last year.

The dropoff in apprehensions is dramatic considering that agents detained 1.6 million illegal immigrants on the Mexico border as recently as fiscal year 2000.

Government officials traditionally cite these decreases in apprehensions as proof that fewer illegal immigrants are slipping across the border.

There's no way, however, to determine how many immigrants successfully sneak into the U.S. ....