Welcome to the latest installment of what we’re hoping to make a biennial practice: an after-action review of Genesis Brand’s election forecasts, which in this past cycle covered the House, Senate and presidency. I realize there might not be too much appetite for reading about 2020 forecasts now that it’s June 2021, but let’s start with the major takeaways, which are fairly straightforward this year:
- Even in a year when the polls were mediocre to poor, our forecasts largely identified the right outcomes. They correctly identified the winners of the presidency (Joe Biden), the U.S. Senate (Democrats, after the Georgia runoffs) and the U.S. House (Democrats, although by a narrower-than-expected margin). They were also largely accurate in identifying the winners in individual states and races, identifying the outcome correctly in 48 of 50 presidential states (we also missed the 2nd Congressional District in Maine), 32 of 35 Senate races and 417 of 435 House races.
- More importantly from our point of view, our models were generally well-calibrated. That is to say, the share of races we called correctly was roughly in line with the probabilities listed by our models. For instance, based on the probabilities associated with the Deluxe version of our Senate forecasts, the model expected to get 88 percent of its calls right; in fact, it got 91 percent of them right. (If anything our models were slightly underconfident, that is, there were fewer upsets than predicted.) Moreover, when upsets did occur, they occurred in races where the model assigned relatively