Markets with only one side
Home runs, first touchdown scorers, and why the maths runs out.
Some markets only let you bet that something happens, never that it doesn't. A player to hit a home run, to score the first touchdown, to score two or more goals. These are usually big prices, and they are usually badly over-juiced, because a book knows you cannot check its working.
Why you cannot de-vig them
De-vigging needs both sides. Scale one number to 100% and you get 100%, which tells you nothing. So there is no mathematically precise fair price on a one-way market, which means no exact EV percentage and no exact Kelly stake.
How to approximate anyway
Line up every book's price on the same market. Say a player's home-run odds run +200, +170, +160 and +140 across four books. The +200 is the outlier worth betting, and you can build a rough fair price by taking the next-best number and adding a deliberate cushion of juice to it. It is a judgement call, not arithmetic, so keep the stakes smaller than the number suggests.
Over 200 bets, the difference between the best price and the worst is $418 — on the identical bet, decided by nothing but where you clicked.
One shortcut: if any book runs a two-way version of the same question, de-vig that instead. A real fair price from a related market beats a guess at an unrelated one every time.
Where the app can't anchor a market properly it says so rather than printing a confident EV. A dash is the app declining to guess.
1 of 3
Why can a one-way market not be de-vigged?
2 of 3
A home run runs +200, +170, +160 and +140 across four books. What is the reasonable move?
3 of 3
What is the best shortcut when one exists?
One-way markets can be beaten by shopping, but never precisely priced. Bet them smaller than the maths suggests.
Terms from this lesson
Education, not betting advice. 21+. Gambling problem? Call or text 1-800-GAMBLER.