Orientation of Betting Odds – Based on True Odds and League Averages
A common approach of bookmakers for setting the draw odds is basing them on the true odds (last 25 matches corrected by the head-to-head (H2H) results, if available). However, if the true odds differ significantly from the league averages from the previous season then a correction factor is applied to the calculations.
Below are two examples of Arsenal home games with H2H history, both from the 2012-13 season.
The screenshots are taken from calculations of the games based on the Value Detector. (Click on the image to enlarge it – opens in a new tab):
Arsenal vs West Brom – 08.12.2012
The calculation of the draw betting odds for Arsenal’s home game against West Brom followed this rule:
Average of the last 25 Arsenal home games and the last 25 West Brom away games, corrected by the results of the H2H matches from the last 10 years with a 50/50 weighting:
(26.00% last 25 matches draw probability plus 14.29% H2H draw probability) divided by 2 = 20.14% [= true Betting Odds: 4.96]
Expected probability [true betting odds] 20.14% plus the average value of the league last season, 24.5%, divided by 2 = 22.3% ==> results in corresponding betting odds of 4.48; then rounded to 4.40
Arsenal won the match 2-0.
Arsenal vs Man Utd – 28.04.2013
The calculation of the draw betting odds for Arsenal’s home game against Manchester United used the following rule:
In this game, bookmakers did not correct the true odds by comparing with the league average because the H2H results showed a probability of 35.71%, corresponding to betting odds of 2.80.
In the above image you can see that the market betting odds for the draw almost exactly mirrored the calculated true odds.
Average of the last 25 Arsenal’s home games and 25 Manchester United away games, corrected by the result of the H2H matches from the last 10 years with a 50/50 weighting:
(20.00% plus 35.71%) divided by 2 = 27.85% [= true odds: 3.59]
Odds setting is mainly about the bookies balancing their books. It is not their goal to predict the expected probability distribution as closely as possible. It is of crucial importance to bookmakers to offer 1×2 betting odds as close as possible to market expectations (= bettors’ expectations).
It can be seen in the screenshot above that Arsenal’s home odds were revised sharply downwards whilst Manchester Utd’s away odds experienced a correction upwards.
This particular game ended in a 1-1 draw, the outsider of the three match outcomes, and since the deliberate odds adjustment probably motivated enough gamblers to back the clear favourite [according to the odds offered, not the ‘true’ probabilities], Arsenal, the bookmakers almost certainly obtained a profit from this match. Of course, the draw was the joint favourite when looking solely at the H2H results over 10 years.
Betting Odds – Based on the Average of the Last 25 Games
In some cases, for example, if the competing teams show a clear tendency not to produce draws against each other, bookmakers then appear to look at the last 25 matches as their starting point for odds setting:
Tottenham vs Newcastle – 09.02.2013
In the above example, betting odds were calculated as follows:
26.00% (last 25 games) plus 24.00% (previous season average) divided by 2 = 25% ==> Betting Odds: 4.00
The true betting draw odds were 7.69, but these are far too high and would have encouraged too many people to bet on Tottenham to win the match than the bookies could feel comfortable with. Therefore they deliberately increased Newcastle’s odds to 5.80 [from 3.75 true odds] and reduced the draw odds to 4.00 [from 7.69 true odds]. This probably stimulated enough people to put their money on the draw and allowed bookmakers to balance their books more easily. As it happened, Tottenham won the match 2-1.
Overall, it can be said that Tottenham are not as simple and straightforward a team to calculate odds for as Arsenal are. Tottenham seldom follow the league averages or their own statistics from the previous season.
In 2010-11 Tottenham finished with an incredible 47.5% of drawn home league fixtures. In 2011-12, their home draw percentage was only 15.8% draws. This constant roller coaster must cause many headaches and guesswork for the odds compilers.
Observing this, it is probably best to skip Tottenham at home when thinking about a portfolio of 1×2 bets.
Laying the draw is a trading strategy, what’s the point of laying the draw and then letting it run? If you are going to do that then surely you would just back the favourite and not have the liability. The whole point of laying the draw is it limits risk, why not do a table of teams who have scored 1st at home and the chance was there to trade out for a profit?
Hi Jamesn,
of course, you are right, there are millions of betting options combining ante post and live betting. However, we at Soccerwidow concentrate on explaining ante-post betting only, specialising on odds calculation. This article is just one example to bring a point across.
We believe that without understanding ante post betting and odds calculation live betting is impossible and pure gambling (meaning – relying on luck only). Live betting requires very fast thinking and calculate probabilities as fast as lightening strikes.
Thank SW! hope you will make some video tutorials like in youtube. Its a good content.
see ya!
Hi Soccerwidow.
1st thank you for sharing your knowledge and for the in depth analyse and explanation.
i want to know 2 things here in the screen shot (the last 25 last game stats and probabilities).
1 – for the home and away calculation Team1 and Team2.
Is it the home and away game winning by T1 et T2 ?
How did you calculate the draw ? only home draw for T1 and away draw for T2 ?
2 – When you say “Best odds” is it the highest odds ? (i use oddsportal)
also i struggle a little bit about to know how my prob.% and odds are good or not VS the bookie.
Thank for reply and good luck:)
Hi Paul,
“Best Odds” are the odds which are available to the individual. People use different bookmaker accounts, and some countries restrict access to bookies. Whatever you use (or can use) are your personal “best odds”.
Regarding calculations… They are fully disclosed to buyers of our Value Calculator: True Odds & Value Detector: League Games with H2H History. The spreadsheet comes with all formulas. However, I have not yet succeeded to write and offer for sale a tutorial (course) which explains calculations and formulas in their depths… Unfortunately, teaching odds calculation requires a lot of explanations and is therefore a very time-consuming exercise. I go forward step by step but it takes time, a lot of time… 🙂