Wisconsin and Simpson's Paradox (and Krugman)

Alright, here goes... I've been silent thus far on the Wisconsin teachers' union situation, in large part because it's a nearly impossible situation in which to take sides. Almost everyone involved seems to be misrepresenting their position, resorting to thug antics, or both.

For my part, I do think that collective bargaining for public unions is a bit of a misplaced concept (a belief that none other than FDR shared), and I think that the "flee rather than negotiate" tactics employed by Wisconsin's Democratic Senators represents a cowardly shirking of their duty, and an attempt to deny the result of any vote that they don't like.

But the Democrats are certainly not the only ones who are negotiating in bad faith. Governor Walker's essential scapegoating of the teachers in this situation misses the big picture--Wisconsin's budgetary woes cannot be solved on this issue alone, any more than our Federal budget can be balanced solely by focusing on discretionary spending. The Governor's actions reek of political opportunism, seizing upon a crisis to push an agenda that is only somewhat related to the matter at hand.

Because I can't resist, Jon Stewart had a fantastic clip relating to my second point, that of political opportunism:

The Daily Show
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Alright, so what does all of this have to do with Krugman and Simpson's Paradox (which has nothing to do with The Simpsons), which I teased in the title of this post? For all of the bizarre and forced rhetoric being spewed by the politicians and protesters in question, the rhetoric in the media coverage has been almost worse. Enter Paul Krugman, my longtime punching bag.

And in low-tax, low-spending Texas, the kids are not all right. The high school graduation rate, at just 61.3 percent, puts Texas 43rd out of 50 in state rankings. Nationally, the state ranks fifth in child poverty; it leads in the percentage of children without health insurance. And only 78 percent of Texas children are in excellent or very good health, significantly below the national average.

While he did not explicitly say so, his implied comparison of Texas to Wisconsin was clear. As pointed out elsewhere, Wisconsin's graduation rate places it 2nd out of 50, blowing Texas out of the water. Collective bargaining must be working, right Krugman?

Unfortunately, there's a fly in the ointment, as pointed out by Eric Falkenstein. It turns out that black students in Texas outperform black students in Wisconsin, white students in Texas outperform white students in Wisconsin, and Hispanic students in Texas outperform Hispanic students in Wisconsin--Texas wins in every category. It just happens that white students, on average, have higher rates of graduation than other ethnic groups regardless of geography, and Wisconsin has A LOT more white students than does Texas.

So while it may look like Texas is struggling to educate its students, it is in fact doing a better job for each ethnic group--it just has the deck stacked against it from an "average" standpoint, because of its drastically different demographics. That's an example of Simpson's Paradox, wherein the omission of an important variable gives rise to a misleading summary statistic.

Krugman, as a Nobel prize-winning economist should (and does) know better, and his laziness on the matter is at best unbecoming. Collective bargaining--or the lack thereof--is probably completely powerless to explain any of the difference in academic performance between the two states; if anything, the more descriptive categorical statistics argue AGAINST collective bargaining. That's bad news for Wisconsin's teachers--or, it would be, if anyone in this mess was actually telling the truth about their intentions.

[New York Times]
[Falkenblog]