We need a more complex analysis of how taxes affect income inequality

One current blogosphere discussion about whether taxes could help reduce income inequality would benefit from more complex analyses. Here is the discussion thus far according to TaxProf Blog:

There have been a number of reports published recently that purport to show a link between rising inequality and changes in tax policy — especially tax cuts for the so-called rich. The latest installment comes from Berkeley professor Emmanuel Saez, Striking it Richer: The Evolution of Top Incomes in the United States.

Saez and others who write on this issue seem so intent on proving a link between tax policy and inequality that they overlook the major demographic changes that are occurring in America that can contribute to — or at least give the appearance of — rising inequality; a few of these being, differences in education, the rise of dual-earner couples, the aging of our workforce, and increased entrepreneurship.

Today, we will look at the link between education and income. Recent census data comparing the educational attainment of householders and income shows about as clearly as you can that America’s income gap is really an education gap and not the result of tax cuts for the rich.

The chart below shows that as people’s income rise, so too does the likelihood that they have a college degree or higher. By contrast, those with the lowest incomes are most likely to have a high school education or less. Just 8% of those at the lowest income level have a college degree while 78% of those earning $250,000 or more have a college degree or advanced degree. At the other end of the income scale, 69% of low-income people have a high school degree or less, while just 9% of those earning over $250,000 have just a high school degree.

This analysis starts in the right direction: looking at a direct relationship between two variables such as tax rates and income inequality is difficult to do in isolation of other factors. While some factors may be more influential than others, there are a number of reasons for income inequality. In other words, graphs with two variables are not enough. Pulling out one independent variable at a time doesn’t give us the full picture.

But, then the supposedly better way is that we were just looking at the wrong variable’s influence on income and should have been looking at education instead! So after saying that the situation was more complex, we get another two variable graph that shows that as education goes up, so does income so perhaps it really isn’t about taxes at all.

What we need here is some more complex statistical analysis, preferably including regression analysis where we can see how a variety of factors at the same time influence income inequality. Some of this might be a little harder to model since you would want to account for changing tax rates but arguing over two variable graphs isn’t going to get us very far. Indeed, I wonder if this is more common now in debates: both sides like simpler analyses because it allows each to make the point they want without considering the full complexity of the matter. In other words, easier to make graphs line up more with ideological commitments rather than an interest in truly sorting out what factors are more influential in affecting income inequality.

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