he most obvious reason America’s presidential candidates are so old might be that Americans are getting older. Voters over 65 routinely go to the polls more often than young voters do, and political-science research has found that voters typically prefer candidates “who are closest to themselves in age.” This sounds like a universal formula: Older countries produce older politicians.

But since the 1980s, almost every European country has gotten older, while the typical European Union leader has actually gotten younger. In the United Kingdom, although people over 55 outvote people under 30 by one of the widest margins in the world, the current prime minister, Boris Johnson, is “only” 55. Biden, Sanders, and Trump are all older right now than the U.K.’s five previous prime ministers, going back to Tony Blair.

So the preference for very old candidates seems to be weirdly, specifically American. What’s that about?

Maybe it’s about decades of youth disengagement from politics. According to The Economist, older Americans have outvoted younger Americans by a wider margin than in the typical OECD country. This is particularly true at the local level. As Timothy Noah writes in Politico, studies have found that the median voter age in America’s municipal elections is 57—“nearly a generation older than the median age of eligible voters.”