Justin Wolfers gives his views about the (now past) differences between the probabilistic predictions given by InTrade on the 2008 US presidential elections…- and the ones generated by the other real-money and play-money prediction exchanges. One hypothesis: US political insiders can’-t access BetFair, legally, and thus can’-t arbitrage. (But they can trade legally on the Iowa Electronic Markets, NewsFutures, Inkling, and HubDub, one could retort.)
Emile Servan-Schreiber’-s hypothesis still holds.
Or else —-your own hypothesis is welcome.
P.S.: The latest news is that InTrade now gives Barack Obama slightly above John McCain.