While we await the conclusion of the weekend's matches and the official prices before the latest, eagerly awaited FTL table is published, here is a post from the Betfair Forum and my contribution to it. The original poster (the astronomy minded Swift-Tuttle) posed this question:
Does anyone have a mathematical proof (or could refer me to one) of why a football match is unlikely to end in a draw?
To put it another way, of the 3 results possible the draw is never favourite. Why not?
Please don't mention those matches in Italy where the Mafia are involved and the draw is a firm favourite. I'm discounting those.
My thoughts on this topic were:
The original poster asked if there was any mathematical proof why the draw can never be the favourite outcome in a match, excluding special cases where a draw will suit both sides such as are seen in late season Italian league matches or in the final game of round-robin group matches.
While it is not a mathematical proof in the true sense of the word, and unlikely to win me a Fields Medal (I’m too old to win it anyway), the answer lies in the fact that any credible football pricing model derives the match odds from goal expectancies, and the only combination of Home Team goal expectancy v Away Team goal expectancy which will result in the draw having the highest probability is when goal expectancy is very low.
If your model uses a simplistic method along the lines of “in the last 20 matches between a top team and mid-table team, 10 matches have been drawn” then you might put the draw probability at 50%, but such a model is fundamentally flawed and no serious punter would ever use such a model.
The probability of a draw is clearly highest when the expectancy of goals is low. Of the under 1.5 goal outcomes, one-third (the 0-0) results in a draw. Add another goal and one-third of the six possible outcomes results in a draw, but add one more goal, and the draw probability drops precipitously. The draw outcomes from the Under 3.5 goal markets total two from ten.
So unless the goal expectancy in a match is two or less, the draw will never be favourite, but the closer to zero the goal expectancy is, the more probable the draw is. The relative lack of interest in the draw as a betting outcome does, in my opinion, make the draw a value bet when the market’s expectation of goals is higher than it should be.
Results from my model show that in 1,823 such matches over four seasons in the top five European Leagues, 565 matches have resulted in draws, an implied draw price of 3.23 which, with the possible exception of the low-scoring Ligue 1, is usually an easily beatable price.