Why betting accumulators aren’t as good as they seem
Every Saturday thousands of people will put an accumulator on that day’s matches, the appeal of accumulators being that the odds soon rack up and large sums can be made from small stakes. The bookies are constantly pushing and promoting them even offering offer such as money back if you are one leg off. Are they a good idea though?
Assumptions
We will start with some assumptions. Firstly the bookies odds are not off for whatever reason (they are generally very good and if not will be corrected by the Wisdom of the Crowd). Secondly that you are betting on a market where you can bet on opposing outcomes (1x2, BTTS, Under/Over etc) which keeps the bookies honest as wisdom of the crowd will correct it.
Bookmaker’s Margin
The first thing we need to do is calculate the bookmakers margin.
I will use Manchester United vs Crystal Palace on the 5th December 2021 as an example using odds from Paddy Power.
For 1x2 the edge is 7.14%, BTTS is 5.92%, Over/Under 2.5% is 8.25%.
From this we can see the bookies margin is usually around 7% give or take for the different markets. (Other games this day are Leeds vs Brentford 1x2 = 6.3%, Tottenham vs Norwich 1x2 = 7.5% and Aston Villa vs Leicester City 1x2 = 7.1%).
Bookies Odds vs Fair Odds
What does this mean though? Well it means you are getting from the bookmakers are worse than the actual odds of the event occurring, which is to be expected as this is how bookmakers make their money.
The odds and fair odds for the Manchester United vs Crystal Palace match mentioned above are in the table below.
What does this mean for accumulators? As the odds for accumulators rack up so does the 7% bookmaker’s margin much like compound interest payments.
Accumulator Legs vs Margin
On a single match you are getting 7% worse odds than the actual real odds of that happening. By the time you get to a six leg accumulator if the bookies are giving you odds of 51.00 (50/1) the fair odds would actually be 76.00 (75/1).
So you can see why the bookies are so keen for you to do accumulators as it increases their margin.
Boosted bets
If you go onto bookmaker’s websites you will commonly see boosted accumulators so lets have a look at one.
We can see here the odds have been increased from 4.00 (3/1) to 4.33 (10/3) although boosts are always good what we want is something to get over the bookies margin. Assuming the odds are good in the first place the odds are actually only 8% better but we know with trebles the bookies margin is up around 22.5% so we are still losing out!
However on the same day we can see this boost from 4.5 (7/2) to 7.0 (6/1) which is over 50% boost in odds and comfortable overcomes the 22.5% bookmaker’s margin. Unsurprisingly the bet is limited to £10!
