Calculate the house edge (vigorish) built into prediction market prices.
House Edge (Vig)
4.00%
This is what the market maker keeps on average
Fair YES Probability
50.0%
Market: 52% (+4.0% premium)
Fair NO Probability
50.0%
Market: 52% (+4.0% premium)
Break-even Win Rate Needed
Vig (vigorish) or juice is the built-in house edge. In a fair market, YES + NO = 100%. When they sum to more than 100%, the difference is the vig.
Example: If YES is 52% and NO is 52%, total is 104%. The 4% vig means on average you pay 2% more than fair value on either side.
If YES + NO < 100%, there's an arbitrage opportunity! Buy both and profit regardless of outcome.