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Nate Silver’s genius isn’t math. It’s journalism.

July 24, 2013

By Ezra Klein

Nate Silver  (Nam Y. Huh/Associated Press)

Nate Silver (Nam Y. Huh/Associated Press)

The news that Nate Silver is leaving the New York Times for a role at ESPN and ABC News (corporate synergies! They’re a thing!) has occasioned some interesting posts on what he got right during the election.

The typical answer to this is, well, “the election.” But getting the election right was no great feat. The betting markets got the election right. The pollsters got the election right. The polling aggregators, like Real Clear Politics, got the election right. The modelers — which included Silver, but also included Sam Wang and Drew Linzer, among others — got the election right. Wonkblog’s election model called the election right — and it did it in June.

The truth is that 2012 just wasn’t a very hard election to call. The polling data all pointed in the same direction, even if many pundits refused to believe what it told them. The secret of the modelers — and it’s not much of a secret — is that they listened to the polling data. Silver et al  got the credit for calling the election right, but the bulk of that credit should really go to the pollsters, without whom none of the modelers could have made any calls at all.

Indeed, one of Silver’s incorrect calls came in the North Dakota race, which Wang called correctly. Why did Wang get it right and Silver get it wrong? Because Wang’s model stuck even closer to the polls than Silver’s model did.

So if all Silver did was build a polling-aggregation model that could call the election correctly on Nov. 1, that wouldn’t be much of a trick. Anyone with access to the polls could’ve done that.

But Silver had two other innovations, both of which are, I think, more important in explaining the appeal — and potential scalability — of his work. The first is that his model begins many, many months before the election, and long before the polls become particularly predictive or frequent. At that point, Silver’s model doesn’t mainly run on polls (it becomes poll heavy as the election nears and the polls become more predictive). It uses ideology and incumbency and economic growth.

I think of that model as a journalistic innovation more than a statistical one. It gave Silver a way to cover the election at a time when everyone knows the polls aren’t worth much but people want to read about the election anyway. It wasn’t, however, a very good model. If you look at Silver’s November 2011 New York Times magazine story, “Is Obama Toast?“,  you see a model that’s way too pessimistic on Obama’s chances.

It concludes, basically, that so long as Mitt Romney is the nominee, “the odds tilt slightly toward Obama joining the list of one-termers.” Even in a scenario where GDP growth was an amazing 4 percent in 2012, it gave Obama only a 60-40 shot over Romney. As it was, GDP growth was 2.2 percent in 2012, and yet Obama never fell behind Romney in the battleground states. I think a fair read of the election suggests that Obama’s chances were much more robust than Silver’s early model indicated. Read more in the Washington Post.


From → Analysis

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