Poverty and income mobility

This month's fedgazette from the Minneapolis Fed features poverty as its theme. There are a number of interesting articles that are worth your attention. In this post, I call your attention to one in particular on income mobility--the ability of individuals and households to move through the income distribution over time.

Income mobility is one of those things that we like to talk about and make claims about. We like to hear stories of "rags to riches", but how often does it really happen? It turns out that we understand relatively little about mobility from a statistical standpoint. Ronald Wirtz writes in the fedgazette article,

Bhashkar Mazumder, an economist at the Federal Reserve Bank of Chicago, has authored several mobility studies in recent years. He said, also via e-mail, that prevailing mobility research throws water on the common notion that U.S. income is highly mobile and more mobile than other countries. More recent studies, like his own, have used much richer longitudinal data that track income over longer periods of time, giving a more accurate reading of lifetime incomes in the United States. Research over the past decade and a half shows that “mobility is relatively low in the U.S. and lower than we thought,” said Mazumder.

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Nathan Grawe has also done research on income mobility as an economics professor at Carleton College in Minnesota. In his estimation, the four best studies done to date on intergenerational mobility have both positive and negative findings, and most results were not statistically significant; in other words, the findings aren't particularly trustworthy. “All told,” Grawe said via e-mail, “I'd say we have no evidence of change.”

Part of the problem is that studies done before about 1990—which generally concluded that the United States had high mobility—are widely discredited today as faulty, mostly because they relied on very small windows of income data, often just a few years or less. In 1992, Solon published one of the first papers suggesting that U.S. mobility was not as high as everyone thought.

Mazumder's research comes to the same conclusion. But his most recent effort with Daniel Aaronson (also of the Chicago Fed) might have something of a silver lining. They found that current mobility might simply be returning to its historical trend line after experiencing an uptick in the 1970s. In other words, mobility might be worse compared to the 1970s, but it might well be in line with the country's historical average.

Obviously, a lack of longitudinal data going way back will remain a problem. Maybe in fifty years we'll be able to put the current period in historical perspective. Too long for some. You know what Keynes said about the long run. While the evidence here is conflicting and the conclusions not quite conclusive, the situation is better than that concerning the question of how much mobility is optimal.

The notion of perfect mobility—an equal chance for any outcome, regardless of where you start—has a hint of social and economic chaos, by virtue of the fact that it implies a lack of predictability in outcomes regardless of the very things that families and societies tend to value: effort, ability, education and other human capital investment, and parenting.

Economists believe incentives motivate behavior. Grawe, from Carleton College, noted that mobility research was often written “in ways which suggest more mobility is better.” But a society with no obvious determinants for income “would clearly have all sorts of incentive problems.”

For example, parents' attempts to offer certain advantages to their kids—reading to them, sending them to better schools, saving for college, transmitting certain values—might be for naught in a world where these things have no lasting economic effect. In a 2002 working paper on the notion of perfect mobility, sociologist Adam Swift of the University of Oxford wrote, “Even those that regard current mobility patterns as evidence of morally unacceptable unfairness should acknowledge that some mechanisms by which parents transmit advantage—or disadvantage—to their children are unobjectionable and would exist even in an altogether just society.”

In other words, there is no clear guidance at all on how much mobility is optimal or even what we mean by optimal mobility. One cannot escape the fact that mobility requires an appeal to long run incentives, but people do not always behave in accordance with those long run incentives. Hence, a divergence between opportunity and outcomes is assured. This is the world in which we live. And this is why the solution to the problem of income inequality is more difficult than many people realize.