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Are Immigrants Really More ‘Fertile’?

8:01 AM, Jun 20, 2013 • By JONATHAN V. LAST
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The total fertility rate, or "TFR," is a statistical construct that attempts to measure how many babies women in a given population set would have in their lifetimes, if all of these women survived through the end of their childbearing years. TFR isn't a particularly hard number—it's really an estimate for a given snapshot in time. (If you want really firm numbers, you’d rather look at "completed cohort fertility," which measures how many babies women in a given age-range actually had during their lifetimes.) But TFR is quite useful for understanding the broad contours of fertility behavior, and on this score, Jeb is exactly right: Foreign-born immigrants have higher TFRs than native Americans.

When you step back from the TFR and look at cruder measures, such as the birth rate—which is just the number of babies born for every 1,000 women between the ages of 15 and 44, you see basically the same picture: Foreign born women have a significantly higher birth rate (87.8) than native women (58.9).

So as a factual matter, what Bush said is unremarkable.

That said, there are two bits of nuance on immigrant fertility that are worth noting.

First, the women who immigrate to America tend to have high fertility rates even by the standards of their home countries. For example, back in 2002, Mexican women had a TFR of 2.4. But Mexican women immigrating to the United States carried with them a TFR of 3.5—meaning that the women leaving Mexico were on the right side of their country's fertility bell curve. The same was true for Canadian immigrants. Canada's TFR average was 1.5; Canadian immigrants to the United States had a TFR of 1.9.

Yet this phenomenon isn’t universal. Immigrants from China, Korea, Cuba, El Salvador, and the U.K. all had fertility rates higher than the average of their home countries. But immigrants from the Philippines, India, and Vietnam came with much lower fertility rates than the average of their sending countries.

Interesting, no?

The more salient fact, however, is that once women come to America, their fertility rates rush back toward our national average at a brisk clip. From 2007 to 2010, for instance, the birth rate for native-born American women declined by 6 percent. The birth rate for foreign-born women declined by 14 percent—more than twice as fast.

I mention all of this because it's worth having as full an understanding of the demographics of immigration as possible.

Now, Bush was highlighting the demographic benefits of immigration in pursuit of a crudely political argument—he wants the Senate to pass the current immigration bill in order to move toward legalization for the 11 or 12 million illegal immigrants currently in America, the vast majority of whom are from Central and South America, particularly Mexico.

And on this subject, it's not clear that Bush’s statement is particularly germane. It's perfectly sensible to argue that the mass immigration we've received over the last 35 years has been a blessing—a mixed one, but a blessing just the same. Yet that has almost nothing to do with the very narrow question whether or not we pursue what amounts to amnesty for a subset of the immigrants who are in the country illegally.

The demographic benefits of immigration are what we should consider in crafting forward-looking policy concerning the system that regulates our immigrant inflows. But that system is separate from the political question of whether or not we should be moving to amnesty the illegal immigrants already in the United States. Because those folks are already here, whether they're eventually amnestied or not. And whether or not we give them amnesty has nothing to do with the extent to which we allow for more (or less) legal immigration in the future.

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