Commercial
Vigorish (Vig)
Definition
The American term for a bookmaker’s built-in margin, expressed through the price rather than charged as a fee. Also called juice. The equivalent concept to overround.
Why it matters
Vigorish is the same idea as overround approached from the other end. A perfectly balanced two-way market would price both sides at even money; an American book prices them at -110 each, meaning a bettor risks $110 to win $100. Those prices imply 52.4% probability each, totalling 104.8%, and the 4.8% above 100% is the vig. The bookmaker does not charge a commission; it is embedded in the odds.
The vocabulary matters when reading cross-market coverage, because European and American writers describe the identical economics in different units and the numbers do not look comparable. It also matters commercially, because vig is the clearest measure of competitive intensity in a market. Standard -110 pricing has held for decades on major American sports, while newer entrants have used reduced-juice pricing as an acquisition tool, and parlays carry far higher effective margins than their component legs. Prediction-market exchanges are a genuine structural challenge here, because an exchange charges a transaction fee rather than embedding a margin, so the headline price a participant sees is closer to the true probability. That comparison is doing a lot of the work in the argument over whether event contracts will take share from sportsbooks.
The bottom line
Vig is overround in American clothing. It is also the cleanest number for comparing how competitive a betting market actually is.