Why some markets are priced far worse than others

The overround on a main line is typically four to five per cent. On player props it is often ten or more, and on exotic markets such as exact scores it can exceed thirty.

Margin tracks uncertainty and liquidity. A market the book prices confidently and takes a lot of money on can be priced tightly; a market it models poorly and takes little on has to be protected with a wider spread.

The high-margin markets are also where mispricings survive longest, because the same thin liquidity that justifies the margin also means fewer people are correcting it. The wide spread is both a cost and a signal.

Here is the catch. A market's margin is never displayed, and the exotic markets that carry the largest margins are the ones presented most prominently.

What to do with it. Calculate the overround of any market before betting it, and require a much larger perceived edge on the wide ones to justify the same stake.

Work it out. The no-vig calculator takes both sides of a market and returns the margin and the fair price of each.