When he officially announced his plan to build a wall on the southwest border in late January, President Trump read the names of five parents in attendance whose children had been killed by people in the United States illegally. The border wall, Trump said, would “save thousands of lives.”

There’s actually no data on the number of Americans killed each year by undocumented immigrants, however. There are about 16,000 murders and 10,000 drunk-driving fatalities in the United States each year, and if undocumented workers were responsible for the same portion of those as the percentage of the US population they represent, that would total about 900 deaths. Some immigration experts think the number is smaller, since most people here illegally come not to commit crimes, but to lay as low as possible and earn money they can send to family members back home.

The wall Trump wants to build to cut down on such crimes will cost at least $21.6 billion, according to government estimates obtained by Reuters. Trump insists Mexico will pay for the wall, but any taxes imposed on Mexico are likely to be borne mostly by American companies and consumers. So here’s the question: If Trump spends $22 billion on his wall, will American taxpayers get a good return on their money?

First, some caveats: Foreigners sneak into the United States in a lot of places other than the southwest border. They walk or drive in from Canada, and arrive by boat and plane. Plus, fences, walls and other barriers already cover 650 miles of the southwest border, along some of the most heavily trafficked areas. The other 1,350 miles, where the Trump wall would go, track less hospitable terrain where few people cross in the first place. So even if it’s fully constructed, the Trump wall might not do all that much to halt illegal immigration.

So it’s reasonable to ask if there might be better ways to spend $22 billion. And if the goal is to save and protect American lives, the answer is possibly yes.

Spending more on drug treatment

The United States spends about $5 billion on drug treatment every year, which is tiny compared with money spent chasing and prosecuting drug dealers. If a fraction of Trump’s $22 billion in wall money were spent on prevention and treatment, it would probably cut US demand for drugs and save lives. “Drug abuse treatment is just crying out for more money,” says Martin Iguchi of the Rand Corp. “The bang for the buck in treatment is more than you’re going to get from any of these other approaches.”

About 55,000 Americans die every year from drug overdoses. Heroin accounts for about 13,000 of those deaths; cocaine, nearly 7,000. Trump himself has called the soaring number of heroin deaths a “tremendous problem” and pledged to do something about it.