One of the most talked-about pieces of economic research in recent years is the Equality of Opportunity project, in which economists used tax data to track the likelihood that American children would move from one income bracket to another over the course of their lifetimes. The team behind it was mostly Americans, such as Lawrence Katz of Harvard and Raj Chetty of Stanford (who was born in India but immigrated as a child). But the focus of that project was on mobility—how to move people out of poverty—not on the growing gaps in wealth. Though the two topics are obviously related, it’s fitting that Americans have taken this approach: Mobility, after all, is central to the American idea, a land where anyone can rise to riches.

Americans also tend to believe that those who are rich have earned it and earned the right to keep it; the nation has lower top tax rates than European nations. Political rhetoric often focuses on protecting rich people from lazy usurpers (think of the phrase ‘makers and takers’), and that shows up in economic thought. Those Americans writing about inequality (e.g. Galbraith, Richard B. Freeman, Jeffrey Williamson, to name a few) focus less on the rich and how much money they have, and more on labor markets, trade, and wage stagnation.

Perhaps the most well-known American economist to focus on inequality was Simon Kuznets (who was born in Belarus). Kuznets theorized in 1955 that inequality would first increase as a country developed, and then decrease over time.

Since Kuznets’ work, though, it has been European economists who have published some of the most well-known work on wealth inequality. A lot of the core work in the field has come out of the London School of Economics, where Piketty completed his Ph.D. “Class conflict is not taboo in Europe, and it was probably even less taboo in the U.K. than in France,” Marion Fourcade, a comparative sociologist at Berkeley, wrote to me in an email.

Why is class conflict more taboo in the United States, a nation dreamed up with at least a bit of rhetoric about throwing off the rigid class structure of Europe? Michael Zweig, an emeritus professor at SUNY Stony Brook, says that American economists haven’t always shied away from social problems like class and inequality. But during the second half of the 20th century, he says, class was “driven from the discipline,” Zweig says. This is largely because U.S. economists focused on the market, always the market.

“In the American economics profession, the scope of economics as a field has been reduced to a study of the market, as though the market was the same thing as the economy,” he told me.

This was perhaps driven, in part, by an appreciation of capitalism during the Cold War. In addition, intellectual work is often strongly shaped by the general social climate. In the 1970s and 1980s, Wall Street’s influence deeply shaped culture; the goal of making tons of money was accepted as normal, even valorized. In general, after World War II, the economics discipline shifted from an appreciation of the government’s role in the economy to a belief that government should stay out of it, Zweig says. Eventually, the issue of income inequality became a “backwater” in American economics, the Washington University of St. Louis professor Steven Fazzari told the New York Times.