Comparing bookmakers cuts the margin from 1.57% to 0.70%

What the margin is

Three prices on a football match imply more than one certainty between them. A book quoting 1.90, 3.50 and 4.20 implies 52.6% + 28.6% + 23.8% = 105.0%, and the 5.0% on top is what it charges for holding the bet.

The six leagues read this morning are tighter than that. The lowest margin at a single book was 1.05%, the median 1.57%, and the widest book on any fixture still only asked 3.26%. Competition has done most of the work already.

What is left after taking the best of each price

A bet does not have to be placed where the rest of it is placed. Taking the best available price on each of the three outcomes and adding the implied chances again gives a median of 100.70% - a margin of 0.70% instead of 1.57%.

On 14 of the 97 fixtures the sum fell below 100%, which means the three best prices together could not lose. Those are listed on the board with the stake split, and most of them were worth under 1%.

Why that is worth more than being right

Halving the margin is 0.87% back on every bet, whatever happens in the match. It needs no opinion, no model and no luck - only an account at more than one book and the patience to compare before clicking.

A pick has to be right to pay. A cheaper price pays on the bets that lose as well, because it costs less to have been wrong.

The part that makes it work less neatly

The best price is rarely at the same place twice. This morning 1xBet held 148 of the 291 best prices, Betfair 34 and Unibet (SE) 28, so capturing them means spreading stakes rather than settling on a favourite book.

Exchange prices are quoted before commission, which is why the board shows what they pay after it. And a price is only a price while it is there: books move lines, limit stakes and refuse them.