Glossary
Overround (margin)
The overround is the bookmaker's built-in margin — the amount by which the implied probabilities of all outcomes exceed 100%.
If you add up the implied probabilities of every outcome in a market, a bookmaker's total is over 100%; the excess is the overround, or margin. A tighter overround means better value for the bettor.
Comparing overrounds across books, and against the near-100% exchange, is a quick read on which book is sharpest on a market — clearer once prices are normalised.
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