WASHINGTON (AP) — President Donald Trump's endorsement of legislation to restrict and reshape legal immigration is based on some shaky assumptions, such as the idea that low-wage green-card holders are flooding in to take jobs from Americans.

Trump swung behind a bill from Republican Sens. David Purdue of Georgia and Tom Cotton of Arkansas, calling it "the most significant reform to our immigration system in half a century" if made law.

A look at statements about the bill Wednesday:

TRUMP: "The current, outdated system depresses wages for our poorest workers and puts great pressure on our taxpayers."

THE FACTS: That doesn't reflect the weight of recent economic research.

Many economists dispute a major study, cited by the White House, that claims low-skilled immigrants hurt wages. Harvard economist George Borjas said the arrival of thousands of Cuban refugees in Miami in 1980 led to lower wages for existing low-skilled workers, but red flags have been raised about his methods. Much of the recent research suggests that immigration has no significant effect on job growth for U.S.-born workers in the long-run.

Most economists also say the benefits of immigration outweigh the costs — a point made in a letter to congressional leaders in April that was signed by 1,470 economists, six of them Nobel laureates.

Researchers have also found that in many states, the benefits of consumer spending by immigrants and taxes paid outweigh any government costs.

In North Carolina, for every dollar spent on health care and education, the economy got $11 back from Hispanic residents in consumer spending and taxes paid — a finding that includes immigrants in the country illegally, said James Johnson, a demographer at the University of North Carolina, Chapel Hill.

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TRUMP: "The RAISE Act prevents new migrants and new immigrants from collecting welfare, and protects U.S. workers from being displaced. And that's a very big thing. They're not going to come in and just immediately go and collect welfare. "

PERDUE: "Over 50 percent of our households of legal immigrants today participate in our social welfare system."

THE FACTS: Over 50 percent is a stretch unless you define welfare in its broadest terms.

About 58 percent of immigrant families with children have used "any welfare," compared with 42 percent of U.S.-born families with children, according to the National Academies of Science, Engineering and Medicine. That includes even subsidized or free lunches offered generally in low-income schools, not specifically to people who have applied for assistance.

As for the food-stamp program known as SNAP, 27 percent of children of immigrants have received such benefits, versus 25 percent of those with U.S.-born parents, according to a Migration Policy Institute analysis of the 2015 American Community Survey.

The National Academies saw little difference between immigrant and non-immigrant families with children when it comes to cash welfare assistance. About 6 percent of families in both groups received such payments.

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TRUMP: "For decades, the United States ... has operated a very low-skilled immigration system, issuing record numbers of green cards to low-wage immigrants."

THE FACTS: He misrepresented who many immigrants are.

Immigrants are increasingly better educated than people born in the United States. This makes them more likely to earn decent incomes and less likely over time to rely on public assistance.

The Pew Research Center said in 2015 that 41 percent of immigrants who had arrived in the past five years held a college degree, much higher than the 30 percent of non-immigrants in the United States. And 18 percent held an advanced degree, also much higher than the U.S. average.

Here's the link to the Pew study: http://www.pewresearch.org/fact-tank/2015/10/05/todays-newly-arrived-immigrants-are-the-best-educated-ever/

The median household income headed by someone with at least a college degree was $94,934 in 2015, well above the national median of $58,044, according to the Census Bureau.

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Galvan reported from Phoenix.

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Find AP Fact Checks at http://apne.ws/2kbx8bd