Hmm looks like 548 gave a 3% chance of R control and betting markets gave about a 15% chance on election night:

https://www.predictit.org/markets/detail/4365/Which-party-wi...

You can also try to work the probability distribution from this betting market and I'm sure they were more favorable to R than he was:

https://www.predictit.org/markets/detail/6669/How-many-House...

That's a pretty big discrepancy regardless, did he ever give an explanation as to why he disagreed with betting markets so much? Seems like betting markets had a ~ one standard deviation pro Trump/R polling error baked into their pricing.

>why he disagreed with betting markets

Because betting markets are kind of dumb? Nate Silver has uttered those words a few times, anyway.

They have a pretty long track record of being predictive.

Not in this case, clearly.

Actually i think the number of seats gained by republicans will be pretty close to the P50 of the betting market probability distribution. They seem to have done better than 538 at least there. It's impossible to verify the overall Biden/Trump victory probability mass function but you could look at state by state races and see who did better.

I don't look through these very deeply but just as an example your link shows that the highest rated prediction on Nov 1st was 242-245 which is actually higher than 538's average.

Yeah I just looked at the distribution on close of Nov 2. The modal bucket was 246+, and the p50 if you convert to a quantitative variable was about 238, which is almost right in line with 538. Ultimately I think the huge difference with betting markets v. 538 for this market was they had higher variance and fatter tails, which could possibly point to a win for 538, EVEN if 538 were legitimately biased!

https://i.imgur.com/O7UegtQ.jpg

We'll simply never know without 1000 realizations of this election but next cycle I'd like Nate Silver to bet money whenever he finds mispriced events/odds and show how much money he makes to strengthen the case that his model is an improvement.