Evidence is mounting that the U.S. is becoming a less attractive place for international students to study.

The latest sign: A report published Thursday by the Council of Graduate Schools, which found that applications from international students to U.S. graduate schools dropped 4% between fall 2017 and fall 2018, the second year in a row of declines. First-time graduate student enrollment is also down 1% for the second year in a row.

CGS views “that result with some concern,” said Hironao Okahana, the associate vice president of research and policy analysis at CGS and one of the authors of the report.

It’s hard to point to a definitive reason why international graduate student applications and enrollment is down, but the political climate is likely playing a role. President Donald Trump famously initiated a ban on people entering the U.S. from multiple Muslim-majority countries, all of which have historically sent students to America to study. U.S. graduate school applications from Iran, one of the countries targeted by the travel ban, fell 27% between fall 2017 and fall 2018.

In addition to the travel ban, the Trump administration has floated changes to student visas that would curtail the amount of time international students can stay in the U.S. What’s more, officials have also reportedly weighed putting more restrictions on Chinese students entering the U.S. out of a concern they may be spying for their home country during their time here.

“We live in very interesting times in terms of U.S. visa and immigration policy,” Okahana said, adding that stakeholders are watching how the policy conversation, political climate and rhetoric surrounding immigration is impacting the flow of students coming to the U.S. to study.

The CGS findings come as colleges and universities grow increasingly concerned about changes to the flow of international students coming to the U.S. Students from other countries enrich the experience of domestic students studying at U.S. colleges and, particularly in the case of graduate students, fill crucial roles in universities’ research efforts, they say.

The U.S. has “certainly taken a hit in terms of reputation of welcoming international students that I think has affected a number of institutions across the board,” said Carolina Figueroa, the vice president of enrollment management at Bentley University in Waltham, Mass. “That has been something that we’re thinking about and continuing to provide as much support as we can to attract these students.”

At Bentley, where nearly 50% of the graduate student population is international, officials have heard from students struggling to get visa appointments, Figueroa said. She’s also heard from international students who say they’re less optimistic about their future here.

“Now they’re thinking more about ‘wait will I be able to go home and find a job?’” she said.

Perhaps one of the most crucial contributions international students bring to the U.S. is money. It’s not uncommon for international students to pay more than domestic students to attend U.S. schools, which can help to subsidize domestic, or in the case of public colleges, in-state students.

Officials at the University of Illinois’ engineering and business schools became so concerned about how trends in international student enrollment could affect their finances that they took out an insurance policy protecting the schools in case of a dramatic drop in Chinese student enrollment.

“We’ve heard from a number of college presidents about declines in international student enrollment and the negative effects it has on institutional budgets,” said Thomas Harnisch, the director of state relations and policy analysis at the American Association of State Colleges and Universities. “The decline in international students has a tangible effect on university budgets, particularly on regional public universities that rely on revenue from these students.”

In addition to the tuition dollars these students provide, they spend money in local communities while they’re here. International graduate students in particular also have the potential to continue contributing after they graduate by starting businesses or work in fields where companies struggle to find qualified workers.

The Institute of International Education, an organization that promotes research and international study, estimates that international students contributed $39 billion to the U.S. economy in 2017.

“International graduate students are pivotal to our economic system, these students go on, many of them earn master’s degrees and Ph.Ds in many highly-needed fields,” Harnisch said. “They’re incredibly important not only to our universities, but our economy as well.”

Though political rhetoric is likely the most prominent explanation for the decline in international students, there are other factors at play. Increased competition from higher education systems in other countries is likely playing a role, Harnisch said.

In addition, developments in students’ home countries can also change the calculus for whether they head to the U.S. for their studies. Okahana cited the example of Saudi Arabia, which tightened its scholarship program for students to study abroad over the past few years.

In India, which, along with China sends the most students to the U.S., currency troubles may be making it more difficult for students to study here, Okahana said. The increasingly tense climate for immigrants in the U.S. may also be affecting the willingness of Indian students to study here. The number of graduate-school applications to U.S. universities from Indian students dropped 12% between fall 2017 and fall 2018, CGS’s report found.

“I do not think that we can overlook some of the incidents around hate crimes towards people of Asian-Indian descent,” he said.