What is the vig (juice)?

The bookmaker's built-in cut. Why sportsbook percentages add up to more than 100.

Ask a sportsbook for both sides of a coin flip and you'll pay 52.4% for each, that extra 4.8% is the vig (also "juice"). It's not a fee on a receipt; it's baked into every price so the house wins whichever way the game goes.

Prediction markets run near-zero vig: YES and NO sum to 100, and exchanges make money on volume fees instead of shaded odds. It's the single biggest structural reason a percent from a prediction market is more honest than a sportsbook line.