A couple of quick pre-election notes:
1. If I could outlaw one type of political journalism, it’d be stories of the form “This election will be decided by voters of Type X” (Rural voters, working-class voters, etc.) In past elections, we were told that the election would be decided by soccer moms, NASCAR dads, security moms, and a host of others.
The problem with these statements is not that they’re false — it’s that they’re true but vacuous. What does it mean to say that the election will be decided by young, unmarried women? It means that, if young, unmarried women tend to vote more than expected for a candidate, then that candidate will win. But in a close election, that’s equally true for all groups.
The problem is that “if more people vote for your guy than the other guy, then your guy will win” doesn’t make for a compelling campaign narrative, so the poor beleaguered horserace journalist has to come up with some novel-sounding theory about some particular group that’s going to “decide” the election. Either that or they could find something useful and important to write about.
2. One bit of good news from the campaign: Bayesian reasoning has gone mainstream. Look at all the attention Nate Silver‘s been getting.
It won’t surprise anyone who knows me to hear that I love Silver’s approach to political analysis. I’ll take a clear model built on data over 100 pundits’ gut feelings.
A number of Republican-leaning types hate Silver, because his model consistently says Obama’s more likely to win. It’s true that Silver is openly pro-Obama, and it’s true that people have a tendency to (consciously or unconsciously) skew things in the direction they prefer. But there are several reasons one shouldn’t make too much of this argument:
- Other quantitative, statistics-based models give predictions similar to Silver’s or even more pro-Obama, as do the betting markets. See, for example, the Princeton Election Consortium.
- Silver’s reputation as a prediction whiz is on the line. His motivation to be accurate is probably stronger than his motivation to boost his guy.
- Silver laid out his methodology explicitly and publicly quite early on, and as far as I know there’s no evidence he’s changed it.
Of course, Silver’s model might be wrong nonetheless. Some people have said silly things like “We’ll know next week how good his model was,” but of course we won’t. As Ezra Klein put it,
If Mitt Romney wins on election day, it doesn’t mean Silver’s model was wrong. After all, the model has been fluctuating between giving Romney a 25 percent and 40 percent chance of winning the election. That’s a pretty good chance! If you told me I had a 35 percent chance of winning a million dollars tomorrow, I’d be excited. And if I won the money, I wouldn’t turn around and tell you your information was wrong. I’d still have no evidence I’d ever had anything more than a 35 percent chance.
One of the sillier critiques of Silver came from Josh Gerstein of Politico:
Isn’t the basic problem with the Nate Silver prediction in question, and the critique, that it puts a percentage on a one-off event?
Of course we use probabilities to describe one-off events all the time. Does Gerstein listen to weather forecasts?
Then there’s the New York Times’s public editor, Margaret Sullivan, who thinks Silver violated journalistic ethics when he offered to make a bet against Joe Scarborough. Scarborough insists that anyone who thinks the race is anything other than a tossup is an idiot, so Silver offered him an even-money bet on the race (with the loser donating money to charity, so neither stands to gain personally).
Sullivan’s point of view on this strikes me as extremely silly. Offering to bet is a standard rhetorical trick when having arguments about probabilities. If you really believe in your probabilistic statement, you should be willing to use it as the basis of a bet.
I don’t think I’ve ever used vulgar language in this blog before, but here goes: by far the best way to put this point is Alex Tabarrok’s line : A bet is a tax on bullshit. If all pundits who opine about the race had to put bets on their predictions, we’d be a lot better off.