Why the closing line is the only honest scoreboard
Whether a bet won tells you almost nothing over a season. Whether you beat the price at kick-off tells you something much sooner, and here is why that is.
Suppose you place forty bets at an average price of 2.00 and win nineteen of
them. Were you good? The honest answer is that nobody can tell. Forty bets at
even money is a coin flipped forty times, and nineteen heads is an entirely
ordinary result for a coin that is fair, a coin that is slightly favourable and
a coin that is slightly against you.
That is the problem with using profit to judge a method. The signal is real but it is buried under a variance that takes hundreds or thousands of bets to settle, and by then the method has changed anyway.
What the closing price knows
The price just before an event starts is the most informed price that market will ever produce. Everything that could be known is in it: team news, weather, the money of every sharp participant, every model anyone ran. It is not perfect, but it is the best public estimate available.
So if you took 2.20 on something that closed at 2.00, you bought at a price
better than the final consensus. Do that repeatedly and it is very hard to
explain by luck, because the closing price does not move because you were
lucky. It moves because information arrived, and you were ahead of it.
Why we publish it
A record of wins is a record that can be curated. Beating the close is measured on every bet, including the losing ones, which makes it much harder to present selectively. It is also the fastest honest signal available, and speed matters when the alternative is waiting a season to learn something.
This is the same argument as what a positive edge actually means, applied backwards: an edge is a claim about a price, so the test of it should be a claim about a price too.
What this does not tell you
Closing line value can be gamed by betting into markets so thin that your own bet moves the price. It also says nothing about staking: a method that beats the close on every bet and stakes badly can still go broke. And a closing price at one book is not the same as the market consensus, particularly at books that copy rather than set.
Common questions
What is closing line value?
It is the difference between the price you took and the price the same bet was available at just before the event started. Beating the closing price consistently means you were early to information the market later agreed with.
Why is closing line value better than profit for judging a method?
Profit over a small number of bets is dominated by luck. Closing line value is measurable on every bet immediately, so it accumulates evidence far faster than results do.
Can you beat the closing line and still lose money?
Yes, over a short run, and it is common. Beating the closing line is a statement about the quality of the decision, not about the outcome of any particular bet.