More on Inequality

Will asks the following question in his most recent post on inequality:

I’ve see no evidence that inequality tends to produce more Democratic voters. Does Jim have some?


I’ve created original analysis that I believe provides direct evidence that more unequal places tend to vote for Democrats, but in the post to which I linked where I reviewed this analysis, I was very careful to say that:

To bound this, however, I should emphasize that this analysis neither supports nor refutes any assertions about causality. Inequality may cause changes in voting behavior, but it is certainly entangled with many other factors.

Trying to build some kind of a cross-sectional model that “holds all other factors equal” is almost certainly a fool’s errand. Interactions between drivers are a central, not a peripheral, component of such a complex social phenomenon. This complexity would overwhelm 3,000 data points pretty quickly. (Professor Gelman, who is one of the best statisticians in America, is acutely aware of this generic issue.)

If anything, the observation that changes in inequality don’t correlate with changes in voting tends to undercut the argument for (simple) causality, though obviously this was pretty crude analysis – I didn’t even have well-aligned time periods, didn’t consider possible lag or confounding effects and so on.

Ideally we would have some kind of structured experiment to establish causality, but it’s pretty hard to see that happening. Barring that, the next best solution would be natural experiments (e.g., look at location-periods with a sudden immigration spike because of some weird legislative change, etc.), but even there it’s hard to see how you would not have deep confounding. Even so, that seems to me to be best bet for some way to disentangle effects.

In my post reacting to Will’s original post, I was responding specifically to Will’s challenge that:

Did Matt not look at the exit polls? Did he not notice that Obama dominated in fundraising among really, really rich people? Here’s a bet for Matt. Take the group that voted for Obama and the group that voted for McCain. Calculate the Gini coefficient for each of those two groups. I’ll bet $1000 dollars that income inequality is higher in the Obama-voting group. If Matt doesn’t want to take this bet, then he needs to explain why divergence in material circumstances poses more of a political problem for Republican coalition-building than it does for the Democrats–the more economically unequal coalition.

I took this to mean, roughly speaking, that Will believes that the hypothesized difference in Gini coefficients between Republican and Democratic voters, if confirmed, falsifies the theory that more inequality tends to produce more Democratic voters. (If Will simply meant that he is agnostic about the causal impact of inequality on voting patterns then I misinterpreted him.)

My response included the delineation of a plausible mechanism by which inequality could help Democrats, which is why I was careful to describe the mechanism in the hypothetical (though, upon re-reading my post, I realize that I should have been clearer about this):

If inequality of condition causes a preference for Democratic policies, then as inequality increases, you will get more Democrats. If it’s a marker for other causes of Democratic voting, then it’s a marker for things that make more Democrats. The idea of a coalition of aristocrats and the proletariat against the petite bourgeoisie and yeoman farmers is not a new one.” [Bold added]

I have not seen compelling evidence that within the normal scope of day-to-day politics in contemporary America inequality either helps or hurts either Democrats or Republicans. I do, however, hold the non-analytically-derived belief that extreme, sustained inequality tends to undermine limited government over time.