Wednesday, March 27, 2013

Amnesty and the Median Voter

As I prepare to introduce my ECO 303 students to the Median Voter Theorem today, I've been thinking about Republicans' worries that allowing more migration from Mexico or amnesty or Puerto Rico into the US will increase the number of Democrats. More of them, fewer of us, we lose elections. The Median Voter Theorem tells me that that isn't the real point to worry about.


To make some simplifying assumptions (aka let's pretend), every immigrant is to the left of every American. Bringing them in not only increases the number of Democrats, it makes the Democratic party more left-wing.

What happens when the Democratic party shifts to the left? Their centrists, moderates, and conservatives feel increasingly left behind. They feel more kinship with Republicans' ideas and start voting Republican. Republican numbers grow also - albeit more slowly and with a lag.

The issue isn't so much that there will be more Democrats (because there will also be more Republicans), but that the political middle will shift to the left. Hotelling's theory shows that both parties will shift to the left as the median shifts lift. The political consensus from both parties will be further from what conservatives want, regardless of which party wins elections.

Does that sound vaguely familiar to anyone complaining that the Republican party have been big spenders in the last decade?

It will also, incidentally, be further from what today's median voter wants. If today's median voter is getting exactly what she wants, she'll get less of it as the equilibrium moves left. Prediction from this simple version of the MVT: not gonna happen. The median voter will oppose letting the consensus move left and so we won't pass amnesty or Puerto Rico or mass immigration.

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