The Statistical Properties of the Electoral College Are Perfectly Bearable

What follows: I give a not-so-ringing endorsement of the Electoral College, by showing that the current mode has reasonable partisan symmetry. I'd still prefer a scheme with the national popular vote, but what we've got ain't so broke.

Andrew Gelman
, Gary King, Jonathan Katz and I published an article on the Electoral College just in time to miss the 2012 US Presidentlal election (here from SSRN and here from the journal website) but apparently just in time to catch the reactions of people complaining about how the election went. Last week, news broke that a group of Virginia politicians wanted to reapportion their state's electoral votes by congressional district, echoing similar attempts in Pennsylvania in 2012 and California in 2008, making it clear that the issue isn't going away any time soon.

In brief, we quantified how much partisan bias there has been in the electoral college system as it stands today (essentially none), if certain states reapportioned in this matter (it depends on the state), and if all states did so (it would have been substantially biased towards the Republicans). In extending the analysis for this post, we find that the Electoral College had no meaningful partisan bias in the 2012 election either.
These recent reapportionment efforts have undertaken by Republican operatives in states where the Democratic candidate has frequently won the state, effectively unbalancing the whole system under the guise of balancing a single state. Our reaction to this wasn't so much whether we thought it was a blatant but short-sighted partisan power grab (of course it is) but what its effect would be on the entire system if more states did this. More to the point, we wanted to check the state of the system as it was at each election, according to the simple question of partisan symmetry:

If one party in a two-party system receives X% of the vote and Y% of the seats, then in the hypothetical situation that the other candidate receives X% of the vote, they should also receive Y% of the seats.
Replace "party" with "presidential candidate" and "seats" with "electoral votes" and you get to  the heart of it; see the paper for details on how we estimate partisan bias. The easiest application of this is if the overall popular vote is tied, then they should expect to receive an equal number of electoral votes. Is this condition present now? Would it be if California or other states split their votes by district? What if every state did it that way?

The paper contains an analysis for each election between 1956 and 2008; for this post, I re-ran the analysis adding preliminary data from 2012 (with a little imputation for as-yet unreported districts) and calculated the effective partisan bias for the election. Zero indicates a symmetric system; a bias of 1 (or -1) would indicate that if the vote were split evenly, the Democratic (or Republican) candidate would win all of the electoral votes available.

As the system stands right now, things are basically fair, and have been from 1980 onwards -- closest to zero is fairest:


If California's electoral votes had been split by congressional district, there would have been some interesting consequences -- not nearly enough of a bump in 1980 to re-elect Jimmy Carter, but a consistent Republican edge ever since.


Suppose we counterweighed this by changing historically Republican Texas to Congressional district apportionment. It would have helped, but not nearly enough to balance the scale:

Now, suppose every state split their electoral votes by Congressional district. The edge is consistently Republican, even today:

In the end, even if other states counter-balanced each other to try and even things out, it would probably make things worse. As things stand, the status quo of the Electoral College is adequate without any kind of large-scale modification, so far as we can predict.


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