Politicians have long engaged in bitter debates over how to stop illegal immigration. But new data from the U.S. and Mexico suggest the problem may be fading away on its own, at least temporarily. Mexican census figures show that net migration to the U.S. border is nearly zero, as fewer Mexicans make the trip north and many who have crossed the border return to Mexico. And the U.S. Border Patrol arrested only 304,755 people trying to cross into the Southwest without papers in the 11 months that ended in August, down from a peak of 1.6 million in 2000. What's behind the "dramatic" change? Here, three theories:

1. America doesn't have enough jobs
The recession is the main reason we no longer have "millions of people streaming over the border," says Abby W. Schachter at the New York Post. The jobs just aren't here any more, so in Mexico, there's suddenly less incentive to say good-bye to loved ones and risk your savings to get into the U.S. Maybe now we can acknowledge that "we need immigrants" — from highly skilled engineers to low-skilled laborers — and finally start discussing immigration policies that benefit everybody.

2. We're kicking out more immigrants than ever
"Enforcement of immigration laws is up — way up," says Rick Martinez at the Raleigh, N.C., News & Observer. U.S. Immigration and Customs Enforcement "is bragging that the agency sent home 396,906 individuals" in the 12 months that ended Sept. 30. "That breaks the previous record of 365,195 deportations" set in 2009. In 2001, that number was just 189,026. The Obama administration promised it would kick out criminals in the illegal immigrant population, and it appears to have delivered.

3. Violent gangs are scaring people away
"Safety in northern Mexico has also become a growing worry for would-be migrants," says Ken Ellingwood in the Los Angeles Times. Gunmen, apparently tied to the ruthless Zetas drug gang, killed nearly 200 people last spring in the northern state of Tamaulipas, and many of the victims were migrants headed for the U.S. "A year earlier, 72 migrants from Central and South America were massacred in the same area." For some Mexicans, the journey to America just isn't worth the risk.