President Trump’s proposed $18 billion wall along the U.S.-Mexico border could cover its own cost if the U.S. cuts off welfare to illegal aliens, a study revealed.

A study from the Center for Immigration Studies found that the $18 billion price tag for the wall along the U.S. southern border could be covered if the U.S. curbed the importation of drugs, crime, and poverty—particularly among illegal aliens who tend to go on the federal government dole.

“The wall could pay for itself even if it only modestly reduced illegal crossings and drug smuggling,” Steven A. Camarota, director of research at the Center for Immigration Studies, told the New York Post.

Federal data shows that illegal border crossings went down 89 percent in El Paso, Texas, over five years after the Bush administration commissioned a two-story corrugated metal fence to be built along the U.S.-Mexico border there.

The Department of Homeland Security estimated that if a wall were not built, there would be 1.7 million illegal border crossings over the next decade.

Camarota said that if a wall stopped 200,000 of those crossings, the country would benefit from fiscal savings from money usually spent on welfare and other benefits spent on illegal aliens crossing the border from Central America and Mexico.

Several other studies have shown that a wall would be beneficial for taxpayers over the long term.

Another CIS study from February revealed that a border wall could save taxpayers $64 billion over the next 10 years.