Bookmaker's Margin

Bookmaker's margin, also known as the "vig" or "overround," is the built-in profit that bookmakers include in their betting odds. When they set odds for an event, they adjust them slightly so that the total implied probability exceeds 100%. This excess ensures the bookmaker makes a profit regardless of the outcome. Think of it as a small cushion or fee embedded in the odds, which guarantees the bookmaker's earnings over time while still offering competitive odds to bettors.