As the number of foreign students at our selective universities exceeds a third of total enrollment, it is important to remember the maxim of the 16th-century physician Paracelsus: “Sola dosis facit venenum.” The dose makes the poison.

From the end of World War II to 1977, the percentage of U.S. university enrollment from abroad never exceeded 2%. With this modest level of foreign enrollment, international students offered significant benefits. They strengthened the education of American students by contributing talent, experiences, and ideas from around the world to the learning environment.

Foreign students also added financial resources to U.S. universities because they tended to pay full tuition and sometimes brought with them large donations from wealthy foreign governments or families. In the context of the Cold War struggle between the Soviet Union and the West, foreign students who learned about the American political system and its values could bring ideas about individual liberty and representative democracy back to their home countries.

After 1977, foreign enrollment at U.S. universities crept higher, slowly at first, before it dramatically skyrocketed over the last two decades. Nationwide, the percentage of international students on college campuses has now nearly tripled since 1977. At our leading universities, the percentage of students from abroad has reached critical mass, averaging about a third but sometimes approaching half of total enrollments.

Among Ivy League institutions, the foreign student population averages 27% or 39%, depending on whether students participating in Optional Practical Training (OPT) program are included. OPT allows foreigners on student visas to remain in the U.S. for as many as three years, if their university recommends that they receive additional applied training by working in their field of study, often as research assistants or instructors at the university. If OPT students are counted, Columbia University now has almost two-thirds of its total enrollment from abroad—a remarkable figure that makes it hard to imagine why U.S. taxpayers are massively supporting the educations of students who aren’t Americans. If OPT students are excluded, international students at Columbia still constitute 40% of its student body.

The University of Pennsylvania, Harvard, and Cornell each number 25% of their enrollment from abroad, not counting OPT students, and between 33% and 37% if OPT students are included. Yale, Princeton, Dartmouth, and Brown all have more than a fifth of their enrollment from abroad, excluding OPT, and between 23% and 31% if OPT is counted.

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What was healthy at a low dose is turning poisonous at much higher levels. As foreign enrollments reach critical mass, the direction of the cultural exchanges taking place on campus has reversed. U.S. students are starting to take political opinions from countries like China, Saudi Arabia, Pakistan, Malaysia, and others whose governments and people are hardly known for their adherence to liberal values like democracy, free speech, legal equality of the sexes, opposition to racism and antisemitism, and other basic rules of the road in Western societies. At a certain level of foreign enrollment, our leading universities stop seeing themselves as the incubators of the American elite and start seeing themselves as incubators of a global elite, which sometimes involves teaching hatred of America and its values.

In addition to direct donations from foreign countries like Qatar, which have proved to be enormous, foreign actors gain leverage over American universities by massive tuition payments that can equal half or more of a given university’s tuition revenue—while helping to make universities unaffordable for all but the wealthiest American families. Foreign actors, whether governments or quasi-official foundations, can advance their agendas both by creating and amplifying entities within universities that promote perspectives preferred by their foreign patrons and by silencing potential critics of foreign misbehavior. Foreign students have played a leading role in campus protests against U.S. backing for Israel in the Gaza war, thereby advancing the foreign policies of their home governments while driving Jewish students off campus.

Neetu Arnold at the National Association of Scholars issued a report documenting how Middle East studies centers at American universities have been “hijacked” by foreign donors. “It is no surprise that foreign governments and individuals fund these centers,” Arnold wrote. “But foreign sponsors rarely need to exercise active influence, for the faculty and staff willingly do their bidding unasked. Donors can thus take a hands-off approach, leaving almost no paper trail other than a dollar amount and a few signatures. The funding still serves their interests: continued production of biased material that promotes the political interests of the donors.”

The Chinese government helped create and fund a network of centers at American universities known as “Confucius institutes,” as a “soft power” tool to advance their interests. Those institutes were so egregious in their propaganda activities, including efforts to silence critics and facilitate espionage, that Congress took action that resulted in the closure of almost all of them.

A more general critique of the influence of foreign money on American campuses is that it has tempted administrators and faculty alike to stray from basic academic norms such as the protection of free speech and the unhindered pursuit of knowledge, free access to university facilities by all faculty and students, the need to prove one’s arguments through objective fact-based research and argument, and prohibitions on violence and intimidation as acceptable methods of argument. According to a study of over 200 universities, “Campuses receiving foreign funds exhibited approximately twice as many campaigns to silence academics as those that did not.” Students at universities receiving more foreign money also reported a greater amount of antisemitic and anti-Zionist rhetoric and activity. The leverage of foreign money has enabled foreign actors to influence the culture and research activity at American universities in significant and harmful ways.

The largest number of international students come from China, which constitutes 27% of those from abroad. Students from India—a country that can at least boast a functioning democracy and which adheres to many, if not all, values of a liberal democratic society—make up 25% of foreign students. A little more than half of these students from China and India are studying math, science, or engineering, but the remainder are spread across a diversity of fields, including those in the social sciences, humanities, and the arts.

As relations between China and the U.S. have become more hostile, there has been a sharp rise in instances where Chinese students have been engaging in espionage against the U.S. and spying on fellow Chinese students to monitor any activity that might be threatening to the communist regime. While these activities of Chinese students in the U.S. pose serious threats to American interests, they do not cause much disruption in the normal operations of universities, which therefore appear happy to let them continue, without disrupting their accustomed cash flow.

Foreign students from countries hostile to Israel, however, have contributed to massive disruptions at U.S. universities after Oct. 7. These protests have not only interfered with regular instruction and research at universities, but they have also forcefully agitated against America and capitalism almost as much as against Israel. In some cases, they have led to the closure of campus facilities and spaces to American Jewish students, and to the cancellation of in-person instruction and graduation ceremonies for all students.

There are 28 countries in the U.N. that do not have diplomatic relations with Israel. Students from those 28 countries represent about 8% of international enrollment. If we add the 11 countries that have recalled their ambassadors or severed relations subsequent to Oct. 7, there are 129,710 students from countries with explicitly hostile relations with Israel, amounting to more than 12% of international enrollment. Other than China and India, both of which have maintained relations with Israel, students from these anti-Israel countries represent the largest block of international students on American campuses.

Universities with a critical mass of international students have hosted many more anti-Israel protests than universities where foreign enrollment is more moderate. A group of researchers at Harvard’s Crowd Counting Consortium tracks protests all over the country. If we focus on the few weeks following Oct. 7 and the last few weeks of the spring 2024 semester, the two periods with the most protest activity, and consider universities with at least 1,000 foreign students, we see a strong connection between the frequency of those protests and schools with high percentages of international students.

We can divide universities into quintiles—five groups, each with the same number of schools. In the three quintiles with fewer than 13% of enrollments from abroad, we see no trend between foreign enrollments and the number of protests. But when the dose is increased so that international students constitute more than 13% of enrollments, the number of protests more than doubles.

Calculations by Jay Greene and Tommy Huska based on data from IPEDS Data Center and OpenDoors and Harvard’s Crowd Counting Consortium

Of course, we cannot prove that high concentrations of international students caused the higher number of anti-Israel protests. Universities with more international students also tend to be institutions with wealthier and more liberal students, factors that other researchers have linked to anti-Israel activity. It is also important to note that the vast majority of international students, like all university students, have nothing to do with protests and just want to focus on their studies. But at higher doses, even a small percentage of international students seeking political agitation can constitute a critical mass to foment significant disruption.

We cannot demonstrate that international students are a large portion of those directly engaged in protests, in part because protesters have gone to extraordinary lengths to conceal their identities, and most reporters and universities have acquiesced to their desire for anonymity. International students have good reason to fear being identified in protests. If those protests violate laws or campus policies, resulting in suspensions, international students risk revocation of their visas and deportation.

Yet it is telling that universities have been visibly complicit in assisting international students in seeking to avoid consequences. For example, MIT publicly announced its reluctance to discipline rule-breaking foreign student protesters for fear that their suspension might cause them to be deported. Most other universities have been very reluctant to call in the police to shut down rule-breaking protests in part out of fear that arrests of foreign students could result in deportations.

Because of these efforts to conceal the role of foreign students in campus protests, we cannot quantify their participation, but we have plenty of anecdotes of their pivotal involvement. For example, Al Jazeera profiled Mahmoud Khalil, a Palestinian raised in Syria who is enrolled at Columbia University. According to that report, Khalil avoided joining the encampment for fear of suspension and deportation and instead took a role behind the scenes as “lead negotiator for Columbia University Apartheid Divest.” Despite his effort to assist the protests without directly participating in them, Khalil was suspended, but that suspension was quickly rescinded. According to Al Jazeera, Khalil “even received a call from the Columbia University president’s office, apologizing for the mistake.” Like MIT, Columbia officials were eager to avoid punishments for international students that might result in deportations.

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The USC Annenberg Media similarly profiled Yousef Khafaja, a Palestinian raised in Germany, who was active in the UCLA encampment. According to that report, “the fear of the consequences he could potentially face as an international student participating in protests has never stopped him from doing so,” then it quoted Khafaja as saying, “Whatever happens to me is not going to be as important as the cause.” But the story acknowledges this sentiment as exceptional, noting “the general fear among pro-Palestinian protesters, who are covering their faces to hide their identity” with concerns about their visa status.

The Washington Post described the experience of two Cornell University international students, Momodou Taal and Bianca Waked, who both served as negotiators for protesters. Despite their efforts to avoid breaking rules by directly participating in protest actions, both nevertheless received suspensions. As they told the Post, they were “only in the encampment area the night before receiving the suspension letter to negotiate with the administration.” Like the claim that there is a distinction between the political and military wings of Hamas, university officials may not believe that negotiators are different from protesters.

Even if the involvement of international students in the protests cannot be fully documented, it is still clear that many foreign students were key contributors to those protests. As the Post put it, “The Post could not verify how many international students participated in the ongoing campus protests. Students at various universities, however, told The Post international students had been playing significant roles as speakers, teachers and general supporters, while avoiding encampments and other areas where the risk of arrest or suspension was high.”

International students have also played a longer-term indirect role in contributing to the wave of anti-Israel protests because many foreign students holding bigoted views imported from their home cultures eventually become professors at American universities where they further normalize hateful doctrines foreign to American culture. For example, Joseph Massad, a Columbia professor who was lambasted during congressional hearings as contributing to the antisemitic culture at the university, had previously been an international doctoral student at Columbia. A critical mass of anti-Israel international students eventually leads to a critical mass of anti-Israel faculty, who in turn recruit U.S. students to their cause. According to a 2019 report by George Mason University’s Institute for Immigration Research, 22% of university faculty are foreign-born, of whom over half remain foreign citizens.

Universities have shown little sensitivity to the potential problem of excess foreign influence. The amount of money they receive directly from foreign students and indirectly from foreign gifts, grants, and satellite campuses is too attractive for them to restrain themselves. And as they become globalized institutions, they feel even less obligation to attend to whether the education they offer serves American rather than foreign interests.

Yet despite all the money America universities receive from abroad, they receive even more from American taxpayers. If U.S. universities prove unable to distinguish between healthy and poisonous doses of foreign influence, policymakers may have to. Certainly, if universities wish to continue receiving large public subsidies, they will eventually be forced to ensure that they are serving American purposes by educating American students in American values and limiting foreign influence over the nature and content of the educations they are providing to foreign- and native-born students alike.