As the immigration debate moves from the Senate to the House, supporters and opponents have been firing claims back and forth. A reader pointed us toward one claim raised by a critic of the bill on CBS’ Face the Nation.

The "so-called path to citizenship amnesty program is a fraction of what the deal bills with," said Dan Stein, who heads a group that opposes the bill, the Federation for American Immigration Reform, or FAIR, on July 7, 2013. "Ultimately, it unleashes a massive increase in overall immigration ... . Essentially, it gives up on the American worker by simply suggesting that at every level of the labor market employers should be able to bring in foreign workers. We're talking about a population increase under the Senate bill of over 70 million people in 20 years -- 70 million people."

The reader wondered whether the bill really "unleashes a massive increase in overall immigration" of "over 70 million people in 20 years." In asking us to check the item, the reader noted that such an increase in the immigrant population would amount to a 22 percent increase over the current U.S. population estimate of 316.3 million, an increase the reader said "sounds implausibly high."

As support for Stein’s claim, Eric Ruark, FAIR’s director of research, pointed us to a paper by the Center for Immigration Studies. While the center has strong opinions on immigration policy -- it’s generally skeptical of expanding immigration -- the group’s study used data from two sources without a dog in the fight, the Congressional Budget Office and the Census Bureau.

The paper noted that CBO, in a recent analysis of the immigration bill, projected that the U.S. will have 16.2 million more people in 2033 as a result of the immigration bill than it would if Congress passed no changes to the immigration system. CBO said this is "primarily because the legislation would loosen or eliminate annual limits on various categories of permanent and temporary immigration."

Meanwhile, the Census Bureau has projected that the U.S. population -- on its own, and in the absence of an immigration bill -- was already set to rise from 316.3 million in 2013 to 365.3 million in 2033. That’s an increase of 49 million.

If you add these two numbers together, you get a roughly 65 million increase in population. That’s pretty close to Stein’s 70 million figure.

Stein’s comments suggested to us, and to the reader who urged us to check the claim, that it’s the immigration bill that caused the 70 million increase. But that’s not the case.

In reality, roughly three-quarters of the 65 million population increase from 2013 to 2033 comes not from additional immigrants crossing the border and having children on U.S. soil, but rather from Americans already legally on U.S. soil having kids, and from immigrants coming to the U.S. legally under current laws. The Senate bill wouldn’t affect this population growth at all.

Several population experts told PolitiFact that they had problems with Stein’s claim.

"I don't see where the 70 million would come from -- certainly not from the countries mostly responsible for undocumented migration," said Douglas Massey, a professor at Princeton University's Office of Population Research. "Together, Mexico, El Salvador, Guatemala, and Honduras account for around three-fourths of all undocumented residents, but the combined population of these countries is only around 150 million. So 70 million (moving here) would represent 47 percent of their combined population, which is simply not credible."

In an interview, Steven A. Camarota, the author of the Center for Immigration Studies paper, declined to assess the adequacy of how Stein phrased the statistic. However, he said it’s not unreasonable to focus on the impact of immigration on the nation’s population growth, even if the number isn’t as high as 70 million.

"The basic question remains: Is 16 million additional residents a lot?" Camarota said. "This is on top of the 19 million from current immigration levels. ... The key question is what are the costs and benefits of significantly increasing the size and density of the U.S. population as a direct result of federal policy? The country lacks even a terse discussion of this issue."

Our ruling

Stein said the Senate immigration bill "unleashes a massive increase in overall immigration. … We're talking about a population increase under the Senate bill of over 70 million people in 20 years."

While credible estimates do say the U.S. population could grow by 65 million between 2013 and 2033, only about 16 million of that would be increases resulting from the Senate bill. The remaining 49 million, or three-quarters of the total, would come from natural population growth among people already in America and by immigration that’s deemed legal under today’s laws -- and thus would have nothing to do with whether the Senate bill passes or not. We rate the claim False.