One thing I don't see mentioned here is PredictIt's advertising approach can bias markets. I haven't done much research into this myself, but a top PredictIt trader mentions in this post that PredictIt advertised on Breitbart during the 2016 election, bringing in lots of money from die-hard Trump supporters: https://politicalpredictionmarkets.com/blog/
Counter-argument: Other prediction markets (that presumably are not mimicking PredictIt's advertising approach) also had similar odds for the 2020 election that were quite far from 538.
One thing I don't see mentioned here is PredictIt's advertising approach can bias markets. I haven't done much research into this myself, but a top PredictIt trader mentions in this post that PredictIt advertised on Breitbart during the 2016 election, bringing in lots of money from die-hard Trump supporters: https://politicalpredictionmarkets.com/blog/
Counter-argument: Other prediction markets (that presumably are not mimicking PredictIt's advertising approach) also had similar odds for the 2020 election that were quite far from 538.