WASHINGTON — Donald Trump’s immigration proposal rests on three assumptions: that immigration hurts American workers; that illegal immigration, in particular, is linked to violent crime; and that illegal immigrants drain government resources. Each of these beliefs is belied by the available academic evidence.

(1) “The influx of foreign workers holds down salaries, keeps unemployment high, and makes it difficult for poor and working-class Americans … to earn a middle-class wage.”

Trump comes closest to having a point in making this case, although the case — that immigration harms the worst-off citizens — does not justify the remedy he proposes.

The laws of supply and demand suggest that a larger supply of labor (more immigrants) will lower wages. But the economic literature points to a counterintuitive conclusion.

“The most recent academic research suggests that, on average, immigrants raise the overall standard of living of American workers by boosting wages and lowering prices,” the Brookings Institution’s Hamilton Project found. “One reason     is that immigrants and U.S.-born workers generally do not compete for the same jobs; instead many immigrants complement the work of U.S. employees and increase their productivity.”

Economists disagree most sharply over immigration’s impact on the wages of the small share of U.S.-born workers with less than a high school education. Here, research by George Borjas and Lawrence Katz of Harvard found that immigration reduced the wages of these workers by 4.7 percent, while another study, by two other economists, Gianmarco Ottaviano and Giovanni Peri, found that wages for this group increased, albeit slightly.

Assume the Borjas-Katz crowd is correct. Even so, if you’re concerned about high unemployment among African-American youth — and you should be — there are far more significant causes, and far more effective ways to tackle that problem than deporting illegal immigrants.

“Overall macroeconomic conditions are a much more important factor in the youth and young-adult labor market than is undocumented immigration,” Katz told me by email. “In fact, attempts to bring undocumented workers out of the shadows … could open up opportunities for such workers in ways that might open more entry-level jobs for teens and disadvantaged minority workers.”

Gordon Hanson, an economist at the University of California, San Diego who has co-authored studies with Borjas, noted that immigration from Mexico is down significantly, so the question is not how to stop the influx, but what to do about those already here.

“If the issue is black unemployment, sending immigrants back home to Mexico is going to have an almost imperceptible effect,” he said. Meantime, the costs would be astronomical.

(2) “The impact in terms of crime has been tragic. In recent weeks, the headlines have been covered with cases of criminals who crossed our border illegally only to go on to commit horrific crimes against Americans.”

The outcry is understandable; the facts prove Trump wrong. Study after study has debunked the notion that increased immigration, legal or illegal, produces a spike in crime. Indeed, the converse may be true.

“Over the past 20 years, during a time that immigration into this country has skyrocketed … there has been no evidence that immigration is linked to positive increases in crime,” said Northeastern University criminologist Jacob Stowell. “Often there is an inverse association: higher immigration means less crime.”

A 2010 study by University of Colorado sociologist Tim Wadsworth found that “cities with the largest increases in immigration between 1990 and 2000 experienced the largest decreases in homicide and robbery during the same time.”

(3) “The costs for the United States have been extraordinary: U.S. taxpayers have been asked to pick up hundreds of billions in health care costs, housing costs, education costs, welfare costs, etc.”

Immigration does strain state and local budgets, particularly for education, in areas where immigrants cluster, although immigrants also pay state and local taxes. But for the federal budget, immigration represents a fiscal plus.

“The consensus of the economics literature is that the taxes paid by immigrants and their descendants exceed the benefits they receive — that on balance they are a net positive for the federal budget,” the Hamilton Project concluded.

Illegal immigrants aren’t entitled to welfare, food stamps, Medicare or Social Security, or unemployment benefits. Indeed, they often pay federal taxes, and contribute more than $12 billion annually to Social Security alone without being able to collect.

Trump is off base — not just in his extreme prescriptions, but in his underlying beliefs. And that is the most disturbing part of this debate, because those wrongheaded assumptions are shared by pretty much the entire GOP presidential field.

Ruth Marcus’ email address is ruthmarcus@washpost.com.