“There are more people living in this country who were not born here than at any time in the history of the country.”

— Rick Santorum on Sunday during an interview on CNN’s “State of the Union”

America’s foreign-born population is already large, and President Barack Obama wants it to grow, former GOP presidential candidate Rick Santorum said Sunday.

Appearing on CNN’s “State of the Union,” Santorum criticized Obama’s recently announced executive action on immigration. Obama’s plan could affect about 4 million immigrants currently living illegally in the United States out of an estimated 11 million total. Under the plan, if illegal immigrants meet certain requirements, they will be able to qualify for a work permit and avoid deportation for a limited number of years.

Santorum warned that Obama’s plan will entice more illegal immigrants, hurting the American-born population that he said is struggling for better employment and wages.

“The last 20 years have been the largest wave of immigration in the history of this country,” Santorum said. “There are more people living in this country who were not born here than at any time in the history of the country. And what the president is saying is, ‘We need more.’ And working men and women are saying, ‘Hold on, what about us?’ “

We found that he is correct in terms of raw numbers, but experts say it’s not the best measure to use when comparing America’s foreign-born population over the years.

We tried to reach Santorum through his PAC, Patriot Voices, but did not hear back.

As of 2012, the most recent year for which there is U.S. census data, the foreign-born population of the United States was about 40 million, which factors in the estimated number of immigrants in the country illegally. That’s the highest it’s been since the census started tracking it.

However, the total U.S. population has grown significantly in the past 160 years. As of 2012, foreign-born residents make up 12.9 percent of the total population. In this respect, today’s foreign-born population is not the highest it’s ever been — in fact, it was higher from 1860 through the 1920s.

Since 1970, when the foreign-born population was 4.7 percent, the trend has been increasing numbers of foreign-born residents. The 2010 percentage of almost 13 percent is the highest it’s been since 1920 and is less than 2 percentage points shy of the all-time high in the 1890s.

Several experts said it is much more useful to measure the foreign-born population as a percentage of the total population rather than absolute numbers.

“As a historian, there is no reason whatsoever to focus on the absolute number over the percentage,” said Kenyon Zimmer, an immigration historian at the University of Texas-Arlington.

Immigrants’ impact on American society is lower today than in 1890, when the foreign-born population as a share of the total population peaked at 14.8 percent. The total population was 63 million, compared with 319 million today (with immigrants making up 12.9 percent).

Of course, differences in the economic and political situations of 100 years ago and today make it difficult to compare immigrants’ impact in any measure. For example, government was smaller 100 years ago, so people had lower expectations for a government-funded social safety net.

Zimmer said the number of foreign-born individuals living in the United States is irrelevant to the current immigration debate. As long as there are jobs available, immigrants will come, legally or not. The estimated number of illegal immigrants living in the United States has gone down by about 1 million over the past decade, and that reflects fewer available jobs following the 2008 recession, he said.

Americans’ attitude toward immigrants sometimes depends on the economic well-being of the native-born population. She compared Americans’ pessimistic outlook today to that of Americans in the late 1800s. Then, Chinese immigrants were seen as a welcome source of cheap labor, until an economic depression struck in the 1870s, bringing widespread unemployment. At that point, many native-born Americans decided they wanted the Chinese out.

Our ruling

Santorum said, “There are more people living in this country who were not born here than at any time in the history of country.”

In terms of the absolute number of foreign-born individuals living in the United States, Santorum is correct.

However, in terms of the number of immigrants as a percentage of the total population, he’s not. Immigrants made up a bigger share of the total population from 1860 to 1920 than they do today. This measurement is by far the more useful of the two, experts said, as it accounts for total population growth.

Whether it’s even worthwhile to compare immigration levels of today with other points in U.S. history is up for debate given drastic economic and political shifts over time.

As for Santorum’s claim, it is partially accurate but missing important caveats.

We rate it Half True.