Moments after Jeff Sessions was sworn in as the nation’s next attorney general, President Trump signed his latest executive orders, creating a task force to reduce crime. Rising crime, the new attorney general said, represents “a dangerous, permanent trend that places the health and safety of the American people at risk.” This grim warning echoes Trump’s remarks to a group of sheriffs that “the murder rate is the highest it’s been in 47 years.”

There’s just one problem. Overall crime rates in America stand at or near lows not seen since the 1960s. There is no national crime wave. But Trump repeatedly tells the American public a different story.

Why does the president—and now the attorney general—blatantly lie so often about crime? Why is this mistruth so important to the administration? Simple: this imaginary crime wave undergirds the president’s most controversial policies—from building a border wall with Mexico, to banning immigrants from Muslim countries, to expanding police presence in cities. Broad belief in “American carnage” is a necessity for his agenda.

Here are the facts: Nationally, crime has been cut in half since its peak in 1991. Murder and violence are near historic lows. In cities once beset by violence, a new generation walks the streets safely.

A warped picture of crime and violence—matched with unconventional, sweeping solutions to this imaginary threat—has been a Trump staple since the beginning.

While announcing his candidacy, the president accused Mexican immigrants of “bringing crime and drugs” into the country. “They’re rapists,” he said. “And some, I assume, are good people.” That, Trump argues, is why his wall with Mexico “is so badly needed.” “Continued illegal immigration presents a clear and present danger,” reads his recent executive order directing the wall’s construction. Last week, the president claimed his wall will “stop the drugs from pouring into our country.”

The same rhetoric underlies his executive order barring immigrants from several Muslim countries. He claims the ban is the only way to prevent an imminent threat of domestic terror attacks. “Call it what you want,” Trump tweeted , the travel ban “is about keeping bad people (with bad intentions) out of the country!” Only this, he says, will “make America safe again.”

This same dynamic holds true on domestic criminal justice policy. Last year, Trump told the Republican convention: “Decades of progress made in bringing down crime are now being reversed by [the Obama] administration’s rollback of criminal enforcement.”

And he’s kept at it as president. “Families don’t feel secure,” Trump said recently to Republican lawmakers. “We have to give power back to the police because crime is rampant.”

What does Trump plan to do in response? Last Thursday he issued three executive orders: to create a commission on public safety, sweep away illegal immigrant “criminals,” and protect law enforcement. One order promises legislation to curtail crime, which may include federal funding for controversial “stop and frisk” policies to be implemented nationwide—a campaign promise. Sessions will also likely end or significantly reduce federal oversight of troubled police departments.

Listening to all this, one would think the country is falling apart and that we need to act fast.

But data from the FBI and several reports from the Brennan Center tell a different story. Like crime, the national murder rate peaked in 1991, and has been cut in half since then. In cities, which the president has called “war zones,” crime has fallen by more than 60 percent in those 25 years.

It’s true that some cities have seen an increase in murders. Last year, the murder rate rose by 14 percent in America’s 30 largest cities — but Chicago alone caused almost half that increase. It’s a mistake to overlook violence in these cities. But it’s an even graver mistake to portray Chicago’s experience as typical. The average person walking down the street today is safer than they have been at almost any other point in recent history.

Unfortunately, the combination of media coverage and repetition makes the president’s claims about rising crime and violence feel true, even when they aren’t. But we can’t let the president’s falsehoods go unchecked. If we allow Trump to succeed at making us feel less safe than we are, we will end up with extreme policies that waste taxpayer money without making us safer.

To be sure, it’s natural to worry about public safety. But solutions to crime and violence must start with an accurate understanding of the problem.

The president, on the other hand, offers solutions without real problems. If the myth of a crime wave were removed, the defense for so many of these new policies would crumble.

These decisions are too important to make based on political rhetoric. Worse, basing policy on “alternative facts” sets a dangerous precedent for our country—one that may be difficult to unwind.

Inimai Chettiar is director of the Justice Program at the Brennan Center for Justice at NYU School of Law. Ames C. Grawert is the John L. Neu Justice Counsel.