This may have Donald Trump pulling his hair.

Not only are Mexicans no longer coming to the United States in large numbers, legally or illegally, more actually are going south than coming here.

That’s the news from the Pew Research Center of migration patterns since the Great Recession hit.

The center’s “analysis of newly available government data from both countries” also found “the overall flow of Mexican immigrants between the two countries is at its smallest since the 1990s, mostly due to a drop in the number of Mexican immigrants coming to the U.S.”

It estimated about 870,000 Mexicans came here from 2009-14, while 1 million Mexicans and U.S.-born children of Mexicans went in the other direction.

The main reason was that the “slow recovery of the U.S. economy after the Great Recession may have made the U.S. less attractive to potential Mexican migrants and may have pushed out some Mexican immigrants as the U.S. job market deteriorated.”

We would add that Mexico’s economy also has been improving the past 20 years, since free-market reforms were implemented after the devastating 1994 peso devaluation, which sent millions of Mexicans fleeing their disastrous economy.

The reforms especially were strong under Presidents Vicente Fox (2000-06) and Felipe Calderon (2006-12) of the National Action Party, which had displaced the sclerotic, long-ruling Institutional Revolutionary Party.

Current President Enrique Peña Nieto is part of the PRI, but has continued the market reforms.

Under Peña Nieto, the country also is moving toward drug decriminalization, which could reduce violence by the drug cartels.

Many Mexicans have fled their homeland to relative safety in the United States. Unfortunately, Mexico’s government maintains strict gun control, not realizing that arming the innocent citizenry sharply drops gun crime.

By contrast, the United States, excepting some tax cuts under President George W. Bush, since 2001 has increased regulations and taxes, producing the sluggish growth of post-recession years.

Pew also found that “stricter enforcement of U.S. immigration laws, particularly at the U.S.-Mexico border, may have contributed to the reduction of Mexican immigrants coming to the U.S. in recent years.”

The basic conclusion of the study is that prosperous countries have fewer problems.

Strange as it may seem, Mexico itself now is an example for Americans of how tax cuts and deregulation bring more freedom and prosperity.