In the United States, while the unemployment rate is relatively low, the Federal Reserve has so far had to keep interest rates near zero to keep unemployment down. It’s the same or worse in many other countries.

Yet economic growth continues, though at a reduced pace, and not just in the United States. According to the International Monetary Fund, real world gross domestic product was 29 percent higher in 2015 than it was just before the recession, in 2007. It has just grown at a lower rate than before, 3.2 percent a year in the eight years after 2007 compared with 4.5 percent a year in the eight years ending in 2007. Perhaps that doesn’t sound like a big enough difference to affect political outcomes.

But the modest slowdown could be a big part of the explanation for the apparent rise of ethnic nationalism, if combined with another factor: rising inequality, along with considerable fear about future inequality.

The numbers are stark. According to the United States Bureau of Labor Statistics, earnings have been basically static. In the bureau’s language, “median usual weekly earnings — in constant (1982-84) dollars (employed full time)” has hardly grown in a generation. The total increase since this data series began in 1979 has been only 1.2 percent, or 0.03 percent a year. The increase has been less than 1 percent since 2007. Even such paltry economic growth is going to the very top, not to the median wage earner. That means that roughly half of full-time wage earners are doing less well in real terms than their parents were.

Benjamin M. Friedman of Harvard University, in his book “The Moral Consequences of Economic Growth” (Knopf, 2005), said that at a deep level people make judgments about the economic progress that they see in their own lifetimes, and in comparison with the progress made by the previous generation, especially their own parents. Few people study economic growth statistics. But nearly everyone knows what they are being paid. If they realize that they are doing less well than their forebears, they become anxious. And if they can’t see themselves and others in their cohort as progressing over a lifetime, their social interactions often become angry, resentful and even conspiratorial.