Why don’t governments in democratic societies do more to combat income inequality?

Scholars have grappled with this question for years. The median voter theory, a longstanding workhorse of political science, predicts that politicians hoping to get elected will seek to close a growing income gap to woo the big bulk of voters in the middle who feel left behind by the fortunate few.

Yet elegant as it is, this idea doesn’t quite mesh with reality. Research reveals little connection between the income gaps in any given country and its government’s effort to close it by taxing the rich to spend on the poor.

There are good reasons why not. The poor vote less than the rich, reducing their electoral clout. And they don’t vote exclusively on the basis of their economic self-interest, but are often swayed by noneconomic issues, like abortion, the environment or gun control.

What’s more, the rich might simply buy political power and use it to maintain their privilege. The political scientist Larry Bartels has documented that the rich have about three times as much influence as the poor on votes in the United States Senate.