Income Mobility and the Social Structure

Okay, let’s get down to brass tacks here in looking at Barton Hinkle’s critique of Jim Webb’s populism. The topic here is one of the most fundamental social questions we can possibly ask—whether or not the American social order is a just one—so it’s worth sinking our teeth in just a bit.

In tackling that question, we need to distinguish between two related yet distinct concerns. The first is whether the basic structure of American society is just or fair; the second is whether the long-term trend in the United States has been towards more or less fairness and equality. This is an important distinction:  if, for instance, long-term trends are static, but the basic structure of society is unjust, then we should be less than heartened to learn that an unjust society is not getting any more just.  

Keeping that in mind, let’s look at the data.

 

The specific data in question here are snapshot analyses of income distribution, divided by quintile, i.e. how much income is the top 20% getting compared to the bottom 20%, and each sector in between? Hinkle, like many others, correctly notes that this sort of snapshot, taken in itself, provides only limited information about the fairness of the overall structure of society.

Why isn’t the snapshot data enough? Because the snapshots don’t provide us information about mobility over time between the quintiles. Consider the child of an affluent family who goes to a selective private college. As a young adult that person might well be in the middle or bottom quintiles of income as he or she finds her feet in the labor market or struggles through graduate school. But eventually that person has a very good chance of making it to one of  the higher quintiles—at least until he or she retires (or gets laid off), when they will likely see income decline.

The quintile snapshot essentially abstracts from all this churning and provides a static shot of how the income distribution looks at a given time. So it’s a limited tool, if we think that we should take not just absolute levels of inequality but also social mobility into account in evaluating the justice of the social structure.

If we compare several quintile snapshots over a long period of time, however, we can garner useful information about the long term trend in the distribution of income, towards more or less inequality. Indeed, looking at how these snapshots have changed over the past three decades produces some striking results:

In 1974, the bottom (poorest) quintile of American families captured 5.7% of aggregate family income; in 2004 that same group captured just 4.0% of such income. In 1974, the top (richest) quintile of American families captured 40.6% of aggregate family income; in 2004 that same group captured 47.9% of such income. Perhaps most strikingly, in 1974 the top 1% of American families, captured 14.8% of aggregate family income; in 2004 those same fortunate few claimed 20.9% of such income. (This data comes from the Economc Policy Institute.)

This is exceptionally strong evidence that the distribution of income in the United States has gotten (just as Jim Webb claims) substantially more unequal over time. In fact, the trend is so strong that it simply is not in dispute among economists and other social scientists who study inequality—in those circles the live debate is not about whether inequality has grown sharply, but what the causes of that growth have been.

Even so, we might not be so disturbed by this growing inequality if it were offset by an increase in social mobility. But how best to measure social mobility?

To answer this question we must again introduce another distinction: between the movement of individuals up and down the quintiles due to variations in income over the course of the life cycle, and between genuine social mobility, in which an individual sees a permanent increase (or decline) in one’s relative position. Conservatives are correct to point out that the income quintiles are not very static over time, with individuals moving in and out of each group all the time, but many (including Hinkle in this case) make the mistake of confusing variation in income over the course of the life cycle—the fact that you’re likely going to make more money in your 40s and 50s than when you’re in your 20s or 70s– with genuine mobility.

The best way to measure mobility is not via snapshots of the whole population, but by tracking a set of individuals over the course of their lives and seeing how they do compared to how their parents did. Economists who undertake such studies have found that, at a minimum, genuine social mobility has not increased over the past generation, and in fact may have actually slowed.

This is important because if mobility has been static, but the distribution of family income has gotten sharply more unequal, than we can only conclude that the American social system as a whole has in fact become more unequal and less fair to the folks on the bottom over the past generation.

But the mobility data can also give us needed insight into the justice of the social structure itself. If you are born into the bottom 10% of families, income-wise, what are your chances of making it out of that bottom 10%? What are your chances of making it into the top 10?

The best recent data on that question comes from Tom Hertz’s study “Rags, Riches, and Race,” which examines mobility among black and white families using data from the Panel Study of Income Dynamics. (The paper is reprinted in the book Unequal Chances: Family Background and Economic Success, the best collection of recent academic work on this set of questions.) 

After adjusting for changes in household size, Hertz finds that if you are born into a family in the bottom decile (poorest 10%) of the income distribution, you have a 36.6% chance of remaining there as an adult, and a 57.1% chance of staying in the bottom quintile. You have just a 2.3% chance of making it into the top quintile, and a mere 0.5% chance (1 in 200) of making it into the top decile.

Conversely, if you are born into a family in the top decile, you have a 26.7% chance of staying there as an adult, a 43.2% of being in the top quintile, and a 77.7% chance of being somewhere in the top half of the income distribution. You have just a 5% chance of falling into the bottom quintile, and only a 1.4% chance of falling into the bottom decile.

In short, if you are born in the poorest rung (decile) of American society, you are over 26 times more likely than someone born in the top rung to stay on that bottom rung as an adult. And if you’re born into the top rung, you’re over 53 times more likely to get there yourself as an adult that someone born on the lowest rung.

Is that fair? Not if you take seriously the notion that America should be characterized by substantive equality of opportunity. (And by the way, from the point of view of African-Americans, the actual picture is even worse than these figures suggest, as Hertz found that upward mobility among African-Americans from the bottom to top quartile was less than half the rates observed among whites.)

Confronting the actual data about intergenerational mobility in the United States forces one to confront some hard truths about the basic structure of this society. Where you start has a huge impact on where you end up, and there is no evidence that it’s getting easier for people to move up. And, as we have also seen, the consequences of ending up near the bottom as opposed to near the top have become more severe, as income inequality has grown over time.

None of those conclusions are controversial among academics who study these questions, and in fact some of those scholars have been trying to ring the alarm on this issue for a number of years. Jim Webb just happened to be the Virginia politican who answered the bell.

Next installment: Do the rich pay too much in taxes? 

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Published in: on November 22, 2006 at 4:09 pm  Comments (2)  

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2 CommentsLeave a comment

  1. The people at the bottom of the income distribution are also less able be heard politically . . . no lobyist, no money, no voice. So maybe nothing will happen? what would happen if the bottom half of the income bracket went on strike?

    p.s. the decline of the middle is maybe the effect of the computer (information revolution). fewer clerks, paper shufflers, etc. are needed to do the same job means lower demand for middle class. conversely, a manager who greenlights a new inventory managment program that is a success can make a lot of money. but it’s kind of a gamble who gets rich and who doesn’t from technology inovation like software etc. Since innovation has such reliance on net effects and lower (almost negligible) costs of reproduction, it results in bigger winners and more numerous losers.

  2. […] Defending Economic Populism, Part One and Part Two Published in: […]


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