In effect, postwar prosperity in America and in Western Europe allowed many voters to shift their political priorities from bread-and-butter issues to less materialistic concerns, “bringing greater emphasis on freedom of expression, environmental protection, gender equality, and tolerance of gays, handicapped people and foreigners.”

Not everyone experienced this newfound economic security, however, and the number of those left behind has grown steadily. Those who do not experience the benefits of prosperity, Inglehart and Norris write, can see “others” — “an influx of foreigners,” for example, as the culprit causing their predicament:

Insecurity encourages an authoritarian xenophobic reaction in which people close ranks behind strong leaders, with strong in-group solidarity, rejection of outsiders, and rigid conformity to group norms.

According to the two authors,

The proximate cause of the populist vote is anxiety that pervasive cultural changes and an influx of foreigners are eroding the cultural norms one knew since childhood. The main common theme of populist authoritarian parties on both sides of the Atlantic is a reaction against immigration and cultural change. Economic factors such as income and unemployment rates are surprisingly weak predictors of the populist vote.

In support of this argument, the authors point to 2016 exit poll data showing that Hillary Clinton won voters who said the economy was the most important issue by 11 points, 52-41, while Trump carried those who said immigration was the most important issue facing the country by nearly two to one, 64-33.

In addition to immigration, issues related to race play a central role.

Inglehart and Norris paraphrase “Strangers in Their Own Land,” the 2016 book by Arlie Russell Hochschild, a sociologist at Berkeley, to show the importance of race in the alienation of many white voters from the so-called liberal culture:

Less-educated white Americans feel that they have become “strangers in their own land.” They see themselves as victims of affirmative action and betrayed by “line-cutters” — African-Americans, immigrants, refugees and women — who jump ahead of them in the queue for the American dream. They resent liberal intellectuals who tell them to feel sorry for the line-cutters, and dismiss them as bigots when they don’t.

Relative — not absolute — economic insecurity plays a major role in the development of these attitudes. Inglehart and Norris observe:

It is clear that strong forces have been working to increase support for xenophobic parties. This seems to reflect the fact that in recent decades, a large share of the population of high-income countries has experienced declining real income, declining job security, and rising income inequality, bringing growing insecurity. In addition, rich countries have experienced a large influx of immigrants and refugees.

They cite the example of Denmark before and after the financial collapse of 2008-9:

In 2004, before the crisis erupted, the overtly anti-Muslim Danish People’s Party won 7 percent of the vote; in 2014, it won 27 percent, becoming Denmark’s largest party. In both years, cultural backlash, rather than economic deprivation, was the strongest predictor of the vote for the Danish People’s Party — but rising economic insecurity made people increasingly likely to vote for them.

There are others making arguments built on Inglehart’s pioneering work on changing values.

Will Wilkinson, a vice president at the Niskanen Center, a libertarian think tank, wrote in a January essay, “A Tale of Two Moralities,” that “an increasing sense of material precariousness can lead to cultural retreat from liberalizing ‘self-expression’ values.” This process helps us

understand why low-density white America turned out to support a populist leader with disturbingly illiberal tendencies.

In sections of the country undergoing sustained hardship — a result of automation, global trade and the residual effects of the 2007-9 recession — the march toward post-materialist values has, in Wilkinson’s view, come to a dead halt.

Wilkinson’s conclusion is based, in part, on his discovery of an unexpected trend in the United States, starting roughly in 2000, which he found evidence of in the series of World Values Surveys.