At his postelection news conference, President Trump said of immigrants traveling to the United States, “I want them to come into the country, but they need to come in legally.” Yet newly released government data show that so far in 2018, the Trump administration is denying applications submitted to the United States Citizenship and Immigration Services at a rate 37 percent higher than the Obama administration did in 2016.

This makes no sense: Depriving immigrants of legal immigration options works against the president’s stated goal of increasing economic growth.

A new analysis for the Cato Institute has found that the Department of Homeland Security rejected 11.3 percent of requests to the immigration agency, which include those for work permits, travel documents and status applications, based on family reunification, employment and other grounds, in the first nine months of 2018. This is the highest rate of denial on record and means that by the end of the year, the United States government will have rejected around 620,000 people — about 155,000 more than in 2016.

This increase in denials cannot be credited to an overall rise in applications. In fact, the total number of applications so far this year is 2 percent lower than in 2016. It could be that the higher denial rate is also discouraging some people from applying at all.

In 2018, the D.H.S. turned away 10 percent of applicants for employment authorization documents compared with 6 percent in 2016, and it rejected applications for advanced parole — which gives temporary residents the authorization to travel internationally and return — at a clip of 18 percent, more than doubling the rate in 2016. Even skilled workers are being rejected at higher rates. The denial rate for petitions for temporary foreign workers shot to 23 percent from 17 percent. The application for permanent workers saw denials rise to 9 percent from 6 percent.

The largest increase in the denial rate for family-sponsored applications, for petitions for fiancés, rose to 21 percent from 14 percent.

Greg Siskind, a Memphis-based immigration attorney with three decades of experience, told me that these numbers back up the anecdotes that he has been hearing from colleagues across the country. The increase in denials, he said, is “significant enough to make one think that Congress must have passed legislation changing the requirements. But we know they have not.”

So what is going on?

Last year, the Trump administration increased the length of immigration applications by double, triple or even more, making them more time-consuming and complicated than ever. This made mistakes far more likely. This year, it also made it easier to deny applicants outright without giving them an opportunity to submit clarifying information. The agency has also made moves to police caseworkers who may be, in its view, too lenient.

Mr. Trump’s political appointees to the D.H.S. have also seized on his rhetorical attacks on immigrants, as well as executive orders like the “Buy American and Hire American” order and another mandating extensive vetting of foreigners, as a justification for a crackdown on legal immigration.

As a result of all this, total immigration to the United States has declined under President Trump, and fewer foreign travelers have been entering the country. These trends are surprising, because the economies of the United States and almost all other countries are growing, which usually generates more travel and immigration. The best explanation for this discrepancy is that the president’s policies are having their intended effect: reducing legal immigration to this country.

This is happening at a time when there are more job openings than job seekers in the United States. This month, Federal Reserve Chairman Jay Powell stated that fewer immigrants and foreign workers would slow economic growth by limiting the ability of businesses to expand.

On some level, President Trump appears to understand this reality, but his policies are making the situation worse.