For several years now, net migration from Mexico has fallen to zero.

What's going on?

Gary Becker, a Nobel Prize-winning University of Chicago economist, writes that it's got little to do with the U.S.

Rather, it's mostly thanks to Mexico and it's growing middle class, as expressed in lower birth rates and rising earnings:

One important cause is the sharp decline in Mexican birth rates during the past couple of decades. Not long ago Mexico was a country with high birth rates that produced many young adults who had trouble finding jobs. Now, the Mexican total fertility rate (TFR)- the number of children born to a typical woman over her lifetime- has plummeted to about 2.25. This rate is only a little above the population replacement rate of 2.1. Unlike in the past, the number of young people in Mexico will no longer be growing rapidly over time, so that the numbers looking for work in the Mexican labor market will be on the decline.

The push from Mexico has also diminished because its economy has been growing at a good clip during the past 9 years. Excluding the large drop in 2009, the growth rate in real GDP has been over 4% per year. Mexico’s growth rate after 2009 considerably exceeds the American rate of under 2%, which is remarkable since about 80% of all Mexican exports go to the depressed American economy. One consequence is that the gap between earnings in Mexico and the United States is narrowing. This clearly reduces the demand to immigrate to America, especially under the difficult circumstances illegal immigrants face.

While a strong U.S. recovery could begin to restart migration inflows, Mexico will grow, no matter what likely rendering the immigration debate academic, Becker says:

the highly controversial American political issue of what to do about illegal immigration should become much less important in the future.

Perhaps we should have seen this coming: it's much easier for Congress to discuss something when there's not as much at stake.