Friday, November 16, 2007

US Income Mobility and Growth

Conflicting data and interpretations are confusing our understanding of personal income growth over the decade of 1996-2005. Politicians are using the data and analyses that support their agenda: are we surprised? My view of the overall media and political landscape is that they are being overly influenced by data and analysis suggesting that US society is becoming more unequal in regard to income and that only certain individuals, generally the already-rich, enjoyed income gains over the last decade.

My colleague Matt Slaughter, recently with the Council of Economic Advisers, likes to point to US Census data from 2000 to 2005 that purportedly shows, in Matt’s words: “income growth has been extremely skewed, with relatively few high earners doing well while incomes for most workers have stagnated or, in many cases, fallen. Only 3.4% of workers were in educational groups that enjoyed increases in mean real earnings from 2000 to 2005…: mean real money earnings rose for workers with doctorates and for workers with professional graduate degrees (i.e., MBAs, JDs, and MDs) and fell for all others.” Surprisingly, the set of workers with just undergraduate degrees had no real income growth between 2000 and 2005.

That sounds pretty bad, and a lot of politicians are using the data to support their claims of rising inequality and the need for some redistributive policies. However, let us be clear about what the data actually show – or more important, what the data do not show. The earnings of workers who had doctorate or professional graduate degrees in 2005was higher than for workers who had doctorate or professional graduate degrees in 2000. Yes. But this does not say anything about any particular individual’s earnings. The people who were in the workforce with doctorate and graduate professional degrees in 2005 were different from the set of workers with doctorate and graduate professional degrees in 2000. The same goes for the set of workers that did not have such degrees – the people in that category in 2005 were not necessarily in that category in 2000. In fact, it is very likely – a certainty – that some of the people without doctorates and graduate professional degrees in 2000 had such degrees in 2005!

So what I have always argued in the face of these data is that they do not say anything about any specific individuals, in regard to changes in their incomes.

This kind of analysis and data can be useful. For instance, if we think the economy is in a steady state, with equal cohorts of people moving through the age and education ranks, then a decline in earnings for, say, undergraduate degree holders would suggest that something is happening to the value of undergraduate degrees. But I don’t think this is the world we live in. The set of people with undergraduate degrees is very different today than it was even five years ago: the mix of degrees is different, the age and experience of the workers is different, and even the gender of the workers is different (and we know there are income differences by gender). The data may only be telling us about the makeup of the set of workers with professional graduate degrees (or undergraduate degrees) and how that makeup differs between 2000 and 2005.

Suppose, for example, that folks with graduate professional degrees were just hitting their peak earning years in 2005, while those with only undergraduate degrees had been hitting their peak earning years in 2000. Then it would be natural to see earnings growth for graduate degrees between 2000 and 2005 and earnings declines for the undergraduate set between the same years (as in 2006, the undergraduate set would have relatively more “early career” workers).

A different study tells a very different story. I first saw the story
reported on the editorial page of the Wall Street Journal, and Matt Slaughter sent me the actual study, “Income Mobility in the US from 1996 to 2005,” which was done by the Treasury. I have not seen any other media references to this report!

The Treasury study tracks the same taxpayers between 1996 and 2005. This analysis is relevant if we are interested in how specific individuals change their income levels, both absolute and relative to others, as they age and gain experience. It is not an answer to the question of “how do people with undergraduate degrees in 2000 compare to those with undergraduate degrees in 2005” but instead to the question of “how much does an average or median worker’s income change over a ten year period?” I think this latter question is extremely important, as to a great extent it is people’s ability to improve their relative and absolute standing that governs their perspective on the overall fairness and justice of the society in which they live.

So what does the Treasury study say? First, that the median taxpayer saw a 24% increase in real income over this period. Second, that about half of all taxpayers who were in the lowest 20% of income earners in 1996 moved to a higher income quintile within 10 years. Third, that the degree of mobility between this decade and earlier decades is basically unchanged. Four, taking the very highest income earners, those in the top 1/100th of one percent, 75% of those were in that category for 1996 fell out of it by 2005 – and the real earnings of that category actually FELL over the period.

The overall picture of the US society from the Treasury study is one of significant movement between income classes, with a general increase in earnings for all classes. This is what we should expect. Ten years ago someone entering the workforce with an undergraduate degree in computer science might be making $30,000. Today they would likely be in the top couple percent of the income distribution.

What would be most distressing to me would be data showing that folks in the lowest income category in one year were extremely likely to still be in that category ten years later. This is definitely not what we see.

Another study worth looking at is the Pew Charitable Trusts study on the Economic Mobility of Families Across Generations. This study looks at the movement across income classes from one generation to another. I will leave readers to look at this on their own, but when I read it, I was very comforted to see the kind of movement from poor to rich and from rich to poor that I think characterizes a truly great society.

No comments: