Between 1995 and 2000, with the U.S. economy booming, nearly 3 million Mexicans migrated to the United States. Taking out the 670,000 that moved back to Mexico, the result was an increase of over 2 million Mexican residents. In 1990, half of those migrants were under the age of 30.

That is probably still a conception that Americans hold about Mexican migrants: The numbers keep increasing as young men cross the border. But it's not quite right.

New data from Pew Research reveals that, since 2009, 140,000 more Mexican migrants left the United States than arrived. That's a faster reverse migration than even the period before and during the recession.

Over the past few years, the number of immigrants from Mexico living in the United States has dropped by more than a million to 11.7 million. Pew also estimates that the number of "unauthorized" Mexican immigrants has dropped from 6.9 million right before the recession to about 5.6 million now.

Why are people leaving? According to data collected by the Mexican government and analyzed by Pew, most returned to Mexico to rejoin their families. Fourteen percent left after being deported.

But the immigrants that remain in the United States also aren't who you might think. Half were under the age of 30 in 1990 — but now a quarter are over 50.

What's more, half of the immigrants from Mexico in the United States in 1990 had been here for 10 years or less. Now, 77 percent of Mexican immigrants have been here over a decade.

There's obvious resonance on this subject with the state of the 2016 election. Even without a big, beautiful wall on the border, the number of documented and undocumented Mexican immigrants in the United States is declining, leaving behind older, more established families. But that doesn't always jibe with the rhetoric.