WASHINGTON >> The economic fallout from Britain’s vote to leave the European Union was swift and stark. The pound cratered to its lowest level in three decades. When the London Stock Exchange opened the next morning, its leading share index immediately fell by more than 8 percent, the largest single-day drop since the 2008 financial crisis.

This was pretty much what financial analysts had predicted. And it is clear from polling data and interviews with voters that those who voted for “Brexit” had been well-warned about the economic risks. They just cared more about something else: immigration.

Most research has found that immigration has bolstered the British economy. But voters supporting the “Leave” campaign either were unpersuaded by the evidence, did not think it had benefited them or felt the downsides outweighed the upsides.

Brexit is not just a blow to the British economy, but also strikes at a core assumption behind the modern liberal order: that voters will act in their self-interest.

The progress of the last 50 years, particularly in Europe, has made it easy to buy into the idea that the forces of nationalism, xenophobia and prejudice are mere irrationalities, market distortions that will naturally fade away in the long arc of history.

Last week’s vote highlighted — not for the first time, but with unusual clarity — the hole in that theory. For many people, identity trumps economics. They will pay a high price (literally, in this case) to preserve a social order that makes them feel safe and powerful.

That dynamic is not limited to Britain, or to this referendum. It is playing out in democracies around the world, and immigration has become its focal point.

Many citizens, particularly those who have suffered under the economic pressures of globalization, express their anxiety over these changes by focusing on another form of change: foreigners in their midst. Halting immigration, even if the actual effect is to worsen their own economic situation, seems like a way of staving off those larger changes.

Democratic governments have shown over and over that they have no answer for this anxiety, even as the stakes, in Europe and globally, continue mounting.

— Facts Cannot Compete With Feelings

Economist Michael Clemens has called immigration a “trillion-dollar bill lying on the sidewalk”: a tremendous increase in wealth waiting to be seized by any country that is attractive to immigrants and willing to welcome them. Loosening restrictions on global labor flows, he argues, would offer a bigger boost to global economies than would dropping all restrictions on trade and capital.

But evidence does not vote — people do. And it turns out that the gains of immigration often feel elusive, whereas the costs can be perceived as heavier than they really are.

A poll released June 20 by Ipsos/MORI showed that 47 percent of voters planning to support Brexit said immigration had been bad for Britain’s economy. Never mind that a study by Britain’s National Institute of Economic and Social Research found that immigration had increased the country’s gross domestic product and had lowered the cost of government services like health care and pensions, which in turn helped reduce taxes.

To be sure, just because immigration is a net positive for the country as a whole does not mean that it benefits all of its people. The geographic breakdown of Thursday’s vote showed that the regions where the Leave campaign fared the best were areas that tend to have few immigrants but also lower wages, according to analysis conducted by Torsten Bell, director of the Resolution Foundation, a British think tank.

This suggests that economic anxiety might be expressed as anti-immigration sentiment even by Britons who have not lost jobs to foreigners.

“You tend to see anti-immigrant sentiment in areas hit by changing economic circumstances or global crises,” said Alexandra Cirone, a fellow at the London School of Economics. “Framing this globalization problem as immigration can also tug on the heartstrings of potential voters, regardless of the actual facts.”

— How Economic Pressures and Demographic Change Blur

So why do people take their economic anxiety out on faceless foreigners? The right answer is probably the simplest one: Immigrants do change their new countries in a million tiny but noticeable ways, even if taking local jobs may not be one of them. Those changes can still be unsettling, even though many changes are undeniably positive.

For people who are already destabilized by economic strain, those social changes contribute to a feeling that something precious is being lost, that their country is turning away from the things they value and toward a new and unfamiliar future.

The Leave campaign spoke to those anxieties by arguing that immigration (which, it sometimes implied, would be nonwhite) had brought Britain to the “breaking point.” British tabloids covered crimes by asylum-seekers in lurid detail and warned that refugees were a “swarm” that could “swamp” the country.

That phenomenon is hardly limited to Britain. In the United States, net immigration from Mexico has been at zero since 2010, but Republican primary voters still cheered Donald Trump’s promise to build a wall on the southern border as though it would solve whatever was worrying them.

— When Anti-Immigrant Backlash Is Expressed at the Polls

Anti-immigrant backlash can play out in several ways. Immigrants may experience xenophobic attacks or be endangered by legal limbo. But the consequences can also be much broader.

Brexit, of course, has shown that there can be severe economic risks. But there are political risks as well. In Hungary, for instance, anti-immigrant sentiment has buoyed President Viktor Orban’s popularity, as well as that of the far-right Jobbik party. Orban has been criticized for restrictions on press freedom and judicial independence.

In Greece, a platform of open hostility to foreigners and slogans like “Greece belongs to the Greeks” have made the neo-fascist Golden Dawn the third-biggest party in Parliament. The party won a half-million votes in the September 2015 election, even though its most prominent leaders were on trial for murder at the time.

A relatively new body of social science research portrays a group of “authoritarians” who are dispersed across demographics but desire conformity, order and social norms. These can be “activated,” as the scholars describe it, when they feel threatened by social change, and then will seek harsh, punitive policies that target outsiders and restore the status quo.

As Jonathan Haidt, a social psychologist and professor at New York University’s Stern School of Business, put it: “It’s as though a button is pushed on their forehead that says, ‘In case of moral threat, lock down the borders, kick out those who are different, and punish those who are morally deviant.’”

Globalization is not going away, and neither are the changes that it brings, including the rise in migration and the division of societies into economic winners and losers. The turmoil created by Brexit may itself become the source of more change, more stress, more instability.