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Quantitative Finance · Glossary

What is Bookmaker, implied probability, overround?

Also known as: bookmaker · implied probability · overround

Definition 27.1 Markets III: Commodities, Energy and Crypto · Chapter 27 — Prediction and Betting Markets

A bookmaker is a firm that quotes odds on the outcomes of an event and takes bets against them as the counterparty. The implied probability of decimal odds oo is 1/o1/o. The overround of a book is the amount by which its implied probabilities over all outcomes exceed one: the bookmaker’s margin.

Methodfavourite (1.50)middle (4.00)longshot (7.00)
Implied, with margin66.6725.0014.29
Multiplicative62.9223.6013.48
Additive64.6823.0212.30
Power64.8222.7112.48
Shin (z=3.0%z = 3.0\%)64.2323.1512.62
Table 27.1. Probabilities, in percent, recovered from a three-way book with an overround of 5.95% by the methods of Proposition 27.2.
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