Chris F. Masse points out Smartcrowd, a blog that gathers prices from several markets as the primary component of its commentary. I’d really like to see a service that only gathers prices for related contracts from several markets in an automated fashion, but Smartcrowd’s apparently manual index on GOP control of the U.S. House is a useful start.
Masse’s summary and comment on U.S. House control contracts are contradictory:
[real-money political prediction markets predict a GOP-controlled House while play-money political prediction markets predict a Dem-controlled House.]
So the crowds at Casual Observer and Newsfutures currently favour Democrats to win the House of Representatives, while the crowds at Tradesports and WSX suggest the Republicans will retain control of the House of Reps.
But WSX is a play-money market.
Aggregation should highlight a problem with play-money markets — play money is not fungible, so one can’t arbitrage between play-money markets, effectively reducing their size. I say should because there’s a pretty big discrepancy between Betfair and Tradesports real-money prices for US. House control. I’m guessing that with more active markets price difference among real money markets would shrink. There should be mountains of evidence one way or the other for sports bets. Anyone know?
By the way, Masse’s collective blog on prediction markets isn’t really launched yet but you may as well subscribe preemptively. Same for his insider blog which has a clever tagline (“the sidebar blog of prediction markets”).
Update 20060926: Masse points out Oddschecker, which does what I want for sports bets (hopefully they’ll expand) and a paper that has some evidence for lack of arbitrage opportunities between real money exchanges. See the comments for details.