Always Above Average

One of the best written and readable blogs out there, is Brian's Betting Tools.

His latest post looks at "What do pro punters/sharps bet on?" and in the sentences on football, and Over / Under betting, are found these words:

What Buchdahl is able to confirm, is that there is a bias towards betting on over 2.5 goals. This isn’t surprising as you can see from forums and twitter that this is a very popular bet but why? Buchdahl explores a few possible reasons for this in his article but the one that stands out is the negative feeling punters get when a goal goes in. It generally feels better for most people to cheer on a goal and turn a bet into a winner than it is to start with a winning bet and it turn into a loser. Particularly for those who get excited by gambling.

Taking the above into account, it did surprise me a little to see fewer prices over even money for the under 2.5 markets, particularly in the Premier League. On closer inspection it seems that the average amount of goals scored in the Premier League is 2.4**, so unders should always be priced below evens on average. Perhaps this is another reason why people prefer to bet on over 2.5 goals. For the recreational punter, betting a tenner or so, the thought of getting less money back than you risk is a bit unexciting and at even money or more you will always win more than you risk.

Joseph's finding (from an admittedly small Pinnacle Tweeted sample of 200 matches last season) was that:

75% of matches witnessed a preference for betting on the Over (betshare greater than 50%) whilst the average Overs betshare was 62%.

Other than the small sample size which Joseph acknowledges in his article, I have an issue with Pinnacle telling us what the betshare is, because the number of bets in themselves is meaningless - what is important and useful to the punter, is how much money is being placed on each side. 

The betshare number could be 99:1 - but if it is 99 mug / square punters ("who get excited by gambling") backing Overs with £10 because the last three matches between the teams in 1908, 1930 and 2009 ended 4:1, 6:2 while one sharp is backing Unders for £990 because their model has a lower goal expectancy than the market suggests, the information is almost useless. (What is useful is that if such a betshare is reported, but the price remains the same, you can deduce that a similar scenario to my exaggerated example is playing out).

I think Brian could have phrased this sentence a little better too:

...the average amount of goals scored in the Premier League is 2.4, so unders should always be priced below evens on average. 

Always be odds-on, on average?  You can't have both "always" and "on average..."

** The average goals per Premier league game is actually a lot higher than 2.4 - since 2015-16 to date it is 2.75, an increase from the 2.66 of the ten seasons prior (2005-15).