We are seeing an outpouring of new empirical work on inequality, led by the economists Raj Chetty of Harvard University and Emmanuel Saez of UC Berkeley. The findings in their two latest papers, written with several co-authors, are casting a fresh light on contemporary political debates.
Perhaps their most striking finding is that in the United States, intergenerational mobility has remained essentially static for about 50 years. Their own evidence focuses on people born between 1971 and 1993. Consider, for example, the probability that children who are born in the nation's bottom fifth will end up (by their late 20s) in its top fifth. For those born in 1971, the probability is about 8.4 percent; for those born in 1986, it is about 9 percent.
In the early 1970s, there was a pretty strong correlation between people's place in the income distribution and that occupied by their parents. That correlation has neither grown nor decreased over time.
All this is nothing to celebrate. If a nation — say, Russia — discovered that it had relatively low intergenerational mobility in 1970, and that the mobility level has stayed constant since then, it wouldn't have a new reason for national pride. But Chetty, Saez, and their co-authors also emphasize that over the last four decades, the U.S. has seen a significant increase in income inequality as well. This increase has important implications for intergenerational mobility.
As the rungs of the economic ladder move further apart, a stable level of mobility becomes a more serious problem, because it matters a lot more whether your parents are rich or poor. The “birth lottery,” as the authors call it, ends up having bigger consequences.
It's one thing if children have an 8 percent chance to get into the top 20 percent, when the top 20 percent isn't so far ahead of the rest of the pack. It's quite different if children have that same 8 percent chance, but the top 20 percent is way ahead of the rest.