There has been much speculation that President Trump’s travel ban and rapidly changing immigration rules would impact tourism to the United States, and it’s already starting to happen.

In 2015, some 78 million people visited the United States, contributing about $200 billion to the economy, or 1 percent of the GDP. In 2016 12.7 million people visited New York City alone. That number is expected to drop to 12.4 million this year. According to a travel expert consulted by The New York Times, those numbers could drop by over 6 million people by 2018, with an estimated loss of $15 billion, compared to 2015.

While the countries subject to the revised version of the travel ban won’t be contributing tourists, many other countries are iffy about people traveling here. A number of people, not coming from those countries at all, have been denied entry to the US, including a New York gallery owner who has been a legal resident for a decade. Confusion has resulted in people who shouldn’t be denied entry being denied, which makes tourists nervous.

Following the original travel ban, inbound travel fell 6.5 percent in eight days, recovering after courts issued stays against it. But they dropped again after the second ban.

Nigeria has suggested that its citizens not visit the United States, because the travel rules keep changing and many Nigerians traveling to the United States have been denied entry.

Indians in the U.S. are discouraging Indian citizens from traveling to the U.S. following an attack on two Indian men near Kansas City, Kansas, which killed one of them. “I appeal to all the parents in India not to send their children to the United States in the present circumstances,” said the father of one of the victims of the attack.

All of these are perfectly valid reasons why people might decide not to visit the United States in the foreseeable future.

The U.S. issues travel warnings about potentially dangerous countries and regions all the time. But now it seems like the United States has joined the ranks of those unsafe nations.