A statistical measure of the profitability of the odds offered by a betting firm on a particular event. To use a simple example, the odds of a coin-toss landing either heads or tails are exactly 50% either way. So the fair odds for heads or tails would be even money for each selection.. A bookmaker would probably offer odds of something like 5/6 (bet £6 to win £5) which represents a 54.54% chance. Adding the percentage odds on each selection together gives us an overround figure of just over 109% (2 x 54.54%). The percentage over and above 100% is the bookmakers potential profit on an event before costs. A betting firm will compile odds in a golf event to ensure an overround figure is reached when percentage odds for each selection are totaled up.

This is profit margin in the bookmaker's favour.