Election Polls Post Mortem
The results of the election are finally tabulated. I have been tracking the polls and Las Vegas odds since the beginning of the year. The first thing that I notice is that on average the polls where mostly accurate within their stated margin of error. The other factor that appears in the final results is that, again on average, the polls were skewed slightly in favor of Biden. The Las Vegas odds were slightly more accurate.
It is interesting to note that Biden won the popular vote with over twice as many votes as Hilary in 2016. The margin for the popular vote was over 6 million votes. The Electoral College vote was the exact reverse of what it was in that year. It was not close, but it was not a landslide. The average of the polls in late October showed Biden ahead by about 4 ½% and he won by almost 4% (as of 11/19/2020). The Vegas odds just prior to the official election day showed Biden as a “slight” favorite.
There were a few areas where predictions were off the mark at the state level. In both Michigan and Wisconsin Biden was favored to win by about 6%. He did win, but by a much smaller margin (especially in Wisconsin where it was less than 1%). Arizona and Florida were both rated as toss ups and each candidate won one of these. Both Vegas and the polls got the Georgia outcome wrong.
On the Senate races the polls and Vegas got the races in Maine and North Carolina wrong and Vegas also missed the mark on Iowa.
All that said, the polls were on target on the vast majority of the races and only erred on the races that were close calls with the exception of Michigan and Wisconsin.