Lets start by looking at how single bets work.
A bookmakers job is to balance their books so that whatever the outcome of an event, they’ll make a profit on that book. This isn’t always the case as sometimes market conditions force them into taking a risk on one or two selections. But in general, this is what they aim for.
What do I mean by “balance their books”?
I’ll explain this with an example. If you take a horse race with 6 runners. A bookmaker will attempt to run this book at approximately 110%. This means that for every £110 they take on the book, they will pay out £100 in winnings to customers, resulting in a £10 profit for the bookmaker. As I mentioned above sometimes they will need to take a hit on a selection, but in general, as customers are betting away on the race, they will be adjusting their prices to hit this percentage.
A rule of thumb is, the more selections in a market, they higher the bookmakers edge will be. So a tennis match might run at 105%, but a first goalscorer market could run as high as 200% and a win-draw-win market in football could be around 107%. This is how bookmakers make a profit.
Now what happens when I place multiples?
If we go back to our horse racing example we know that on average, for every £110 you place in single bets on horse racing, you’ll receive £100 back which means that in the long run you lose £10 for every £110 you place.
The part that the bookmakers do not want you to know is, if you place a double on horse racing with two markets running at 110%, you are multiplying the bookmakers edge (1.1 x 1.1 = 1.21 or 121%). This means that for every £121 you place in doubles, in the long run you will get back £100 and lose £21. Just by placing a multiple bet you are giving the bookmaker a bigger edge.
This means that those £10 accumulators you place at the weekend might be fun, and on the rare occasion when you hit one the payout is nice, but on average over time you are getting hammered. Even if you do your research on the selection to minimise the edge of the bookmaker, you still cannot research your way out of the growing and growing edge that happens with every extra selection you add.
To explain it in everyday terms. If you place a £10 single on an evens shot every weekend, you will, over the course of the year make far more money than someone placing a £10 accumulator every weekend. You won’t be able to brag about a £20 return on a £10 single bet as much as someone can on a £80 return off a multiple bet, but you will have many, many more winners and in the long run, make more money.
How do I ensure I maximise my chance of winning?
Be disciplined and place SINGLE bets on well researched selections. These will mostly be low odds, but who cares when you are making money every week.