Reading T20 odds without getting fooled by them

Two teams are about to play at Kensington Oval and both are quoted at 1.90. Most people read that as the market saying it cannot separate them. That is half right, and the missing half is where the money goes.

Start with the formats, because they describe the same thing in different clothes. Decimal odds tell you what a winning unit returns in total, stake included: 1.90 means one unit back becomes 1.90, so the profit is 0.90. Fractional odds quote the profit only, so the same price is roughly 9 to 10. Neither is more accurate. Decimal is easier to compare quickly, which is why almost everyone pricing cricket uses it.

The useful move is converting a price into a probability. Divide one by the decimal odds and you get the implied probability. At 1.90 that is about 52.6 percent. At 2.50 it is 40 percent. At 1.25 it is 80 percent. Once you are thinking in probabilities rather than returns, a price stops being a payout and becomes a statement about the world, which is what it actually is.

Now do it to both sides of that even market. Each side implies about 52.6 percent, and together they imply about 105 percent. Probabilities cannot sum to more than a hundred, so the extra five points are not a claim about cricket. They are the operator's margin, usually called the overround, and they are the price of being allowed to bet. This is the thing that is hidden in plain sight in every market you will ever see, and adding up the implied probabilities takes fifteen seconds and tells you precisely what you are being charged.

The practical consequence is that margins are comparable and worth comparing. A market summing to 102 costs you less than one summing to 108, on every bet, whether it wins or loses. Thin markets carry wider margins because fewer people are pricing them, and women's franchise cricket is a thin market by any measure. That is not sharp practice, it is what happens when a market has less money in it. It does mean the difference between one operator and another is larger here than on a major men's fixture.

The final thing to unlearn is treating a short price as a prediction. A side quoted at 1.30 is not going to win. The market is saying that if this fixture were played a large number of times, that side would win around three quarters of them, which also means losing a quarter. Short-priced teams lose constantly and the market is not wrong when they do. In a four-team round robin where each side plays three group matches, the sample is so small that even a well-priced favourite can miss the final without anything unusual having happened. Prices describe distributions. They do not describe Tuesday.