PolitiFact's Jon Greenberg  [Email him] has an item that says Ann Coulter wrongly claims that U.S. 'has already taken in one-fourth of Mexico's entire population', By  June 2nd, 2015.

When Ann Coulter wrote in a recent syndicated column, that

“America has already taken in one-fourth of Mexico’s entire population.”

I added a link to a 2011 column where I said much the same thing:

“Today, about a fifth of all Mexicans in the world live in the US.

And that was linked to a 2005 Sailer column which said

There are currently 106 million people in Mexico and approximately 25 million people of Mexican descent in the United States. In other words, just under 1/5th of all Mexicans in the world now live in America. And they got here without an official open borders plan.

But I could have just linked to Wikipedia, which says, in the article on “Mexican-Americans “

The United States is home to the second largest Mexican community in the world second only to Mexico itself comprising over 24% of the entire Mexican origin population of the world.

Wikipedia’s source is the US Census. Ann Coulter sourced a  Pew Research Center report in her book.

So what's Greenberg's argument? He's saying that Mexicans aren't Mexican.

In reality, the immigration data from Pew is not nearly as neat and tidy as Coulter concludes. The Pew report attempted to count the number of people who trace their roots back to Mexico, not people who came directly from that country.

Why does that make such a difference?

Well, about two-thirds of Americans with Mexican ancestry were born in the United States. By definition, they were never part of Mexico’s population.

If they weren’t Mexican, they could not be "taken in."

But they are Mexican. They say they're Mexican, and the Government of Mexico thinks they're Mexican. Many of the Mexicans born in the US are born to Mexican parents who are citizens of Mexico, and they can go to Mexico and claim citizenship there if they want.

What we're looking at is colonization. Citizens of Mexico move to the US, live in barrios and colonias, and raise their kids in America, and the so the Mexican population grows until the number of Mexicans in America is equal to, as Ann Coulter says, 25 percent of the population of Mexico.

A much shorter answer to Greenberg  is the graph at the top of this post. In 1950, America had 4 million Hispanics. The difference between 1950 and 2015 is due to immigration, not natural increase.