MickyB, on Oct 7 2008, 12:53 AM, said:
Despite a pretty big lead for Obama in the polls, the bookies seem to think he is only about 75% to win. Is this because it takes a relatively small percentage of voters to change sides to swing it, or because there's a belief that some people are saying that they will vote for Obama because they think doing otherwise would make them appear racist? Or something else that I've missed?
It may be a little tricky to decide exactly what this 75% figure means. I'm guessing, for starters, that this means something on the order of: If I want to place a bet with the bookies, I can place a bet for $3 on Obama, winning $1 from the bookie if Obama wins, or I can place a $1 bet on McCain, winning $3 from the bookie if McCain wins. Obviously there would have to be some transaction costs but this would be the core. In theory, this would mean that if we ran the probabilistic event a zillion times and McCain won a quarter of the events, the bookies would break even on the bets and pocket the transaction costs. But it really isn't a probabilistic event and we won't be running it a zillion times so I assume the odds really reflect the market. Let's say the transaction cost is ten cents on the dollar. Then the bookies find that they can get people to bet the $3.30 on Obama and others to bet the $1.10 on McCain in roughly the numbers that are needed so that whoever wins they come out fine.
I know virtually zip about how bookies make their living but if anything like the above is true then the bookie odds do not reflect their judgment of who will win but rather the broad market judgment of who will bet what at what odds.
One could try a thought experiment: Suppose I offer a bet (I am not doing so, this is suppose). I'll take McCain. If Obama wins, I'll give you $500. If McCain wins, you give me $1500. Would you take the bet? Suppose it is $500 versus $2000, or $500 versus $2500. Where would you stop taking the bet? Where would you say that while you prefer Obama, at the offered odds you will place your bet on McCain?
The bookies may have it about right. I would consider betting $1500 on Obama, winning $500 if Obama wins, losing my $1500 if Obama loses, but I wouldn't go much higher.