Betting exchanges are becoming more and more popular. The odds on offer on the betting exchanges are generally higher than those offered by 'traditional bookmakers'. But, what is a 'fair' price for a horse with a SP of say 10-1.
I have analysed the proportion of
horses which actually win at different odds. I have calculated what
the true odds should be for each value of SP odds.
Click on the links on the
left for details.
This above indicates that there were 8,352 horses which started at odds of 3-1. Of these, 1,890 actually won the race. So, 22.6% of them won. If you had backed all 8,352 of them (with the same stake) you would have got a return of 90.5%. This represents a loss of 9.5% of stakes.
Most betting exchanges express odds as decimals. The decimal equivalent of 3-1 is 4.00. The 'true decimal odds' of something which happens 22.6% of the time is 4.42. So, the 'fair' price for horses with a SP of 3-1 is 4.42 (or 3.42-1). This is the sort of price which you should expect to take (or lay) on a betting exchange.
Click on the links on the left for the full tables. They show that the differences between the SP odds and the true odds increases as the odds get bigger.