My argument doesn’t require the EMH to be true in any strong sense, just true enough that you can’t beat a big, liquid market by a large margin via easy analysis of very public information. Predictit’s price is similar to Betfair’s—in fact Betfair is currently slightly less favourable to Biden—and presumably won’t diverge too far in either direction due to arbitrage. Betfair has matched about $180 million on its ‘next US President’ market. Of course a lot of its users are wild gamblers, but it is big enough to attract serious professionals (and smart opportunists with plenty of capital) too.
My argument doesn’t require the EMH to be true in any strong sense, just true enough that you can’t beat a big, liquid market by a large margin via easy analysis of very public information. Predictit’s price is similar to Betfair’s—in fact Betfair is currently slightly less favourable to Biden—and presumably won’t diverge too far in either direction due to arbitrage. Betfair has matched about $180 million on its ‘next US President’ market. Of course a lot of its users are wild gamblers, but it is big enough to attract serious professionals (and smart opportunists with plenty of capital) too.