… Polls and forecasts, including FiveThirtyEight’s forecast, were highly accurate and did about as well as you could expect. So let’s go through how our forecast, in particular, performed: I’ll brag about what it got right, along with suggesting some areas where — despite our good top-line numbers — there’s potentially room to improve in 2020.
But before I do that, I want to remind you that our forecasts are probabilistic. Not only are our forecasts for individual races probabilistic, but our model assumes that the errors in the forecasts are correlated across races — that is, if one party’s chances were overrated in one race, they’d likely be overrated in many or all races. Because errors are correlated, we’re going to have better years and worse ones in terms of “calling” races correctly. This year was one of the better years — maybe the best we’ve ever had — but it’s still just one year. CONT.
Nate Silver, FiveThirtyEight