Since I don't have US Passport yet, and I don't know how legal internet gambling is, I won't pursue the following strategy, but, out of curiosity, where do I make a mistake?
I noticed that you can sell contract against Obama on Betfair.com at a rate 1.44/1 (i.e., you pocket $1,000 and create liability in Obama wins at $1440) with a reasonable depth (when I looked at it, you could enter more than $3,600 worth of such contracts). BTW, that rate implies almost 70% of Obama victory.
At the same time, Intrade prices on Obama are around 63%. I believe if I bought $1,000 of Obama contracts, based on the depth I'd probably pay an average price of 63.5%
So here is my strategy:
Sell $1,000 against Obama on Betfair, and immediately hedge the potential payout by buying $1440 worth of Obama contracts at the price of $1440*0.635 = $914.40
So, right now, I pocket $1,000-$914.40 = $85.60
I also know Betfair takes 5% of the profits, while Intrade charges a very small fixed monthly fee, but no profit cuts (I think it's $20, but I'll consider it a sunk cost of being on Intrade, and probably trading like crazy).
If Obama wins:
I make loss with Betfair (so no payment to them), and I pay the BEtfair counterparty with my $1440 I won on Intrade. I keep the 85.60 I made today
If Romney wins:
I make $1,000 profit with Betfair, they take 5% ($50), I am thus left with $85.60-$50 = $35.60
Either way, I make a pretax return between 8.56% (if Obama wins) and 3.56% (if Romney wins) - risk free, instantaneously. With the possibility of repeating, until the both prices converge. Even if I have to keep my money deposited, that market will close very soon, with elections 1 week away.
Now, I would think that in terms of taxes on winnings, I pay the taxes on the NET profits (profits - losses), i.e. I'd be taxing either $85.60 or $35.60.
Where did I make a mistake? (Otherwise I see no reason why people would not do this already.)



