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Polling aggregators like @NateSilver538 at @FiveThirtyEight are making the same mistakes they made in 2016, giving poor-performing state level polls too much weight. Consequently, they exaggerate the odds of a Biden win at 87% (they gave Clinton 71% odds). 1/
I& #39;ve been digging into their data to understand the election. First, kudos to them for making everything available and taking-on hard work. This is meant to be constructive criticism.
There is a very weak relationship between how they grade pollsters & 2016 performance
There is a very weak relationship between how they grade pollsters & 2016 performance
This matters because their polling aggregations and prediction models give more weight to pollsters with better grade, but their grading system is not well-aligned with 2016 performance at the state level.
Even worse, their grading system seems to be biased against pollsters that show large Trump margins in 2016 relative to actual. I took the difference between a ranking based on 2016 results & their poll ranking. Their rating bias was pro-Democratic Party.
Take a concrete example. 538 gives @trafalgar_group one of the worst ratings in their system (11/15), but they should be in the best group based on their 2016 performance. They had very low errors & correctly called MI, FL, and several other swing states no one else got right.
As it plays out, 538& #39;s models give Biden several swing states (AZ, NC, FL, and MI) that Trafalgar has Trump leading. 538 is using polls that had a pro-Clinton bias by a large margin in 2016 & giving them more weight than Trafalgar, without any obvious correction.
Given these results ( https://www.thetrafalgargroup.org/ ),">https://www.thetrafalgargroup.org/">... it seems highly misleading to say that Biden has a 87% change of winning. These swing state polls are much tighter than a superficial reading would suggest based on 2016 performance. I don& #39;t have any confidence one way or another.
