Looking at the Starting Price Overrounds in 2025
By Steve Tilley
I used Proform to study overrounds in 2025. The overround shows how much extra is built into the betting prices.
To make things fair between races with different numbers of horses, I divided the overround by the number of horses in each race. I called this Overround Per Horse, or OPH.
Other things can affect the overround, such as place betting and odds on favourites. But these things usually stay fairly steady during the year. So OPH is a reasonable way to measure changes.
I then worked out the average OPH for each week of 2025.
What the Data Shows
At the start of the year, the average OPH was about 0.0195 per horse. By the end of the year, it was almost 0.022 per horse.
The weekly line moves up and down quite a bit. So, I added a smoothing line to make the overall trend easier to see.
The smoothed line shows that OPH was fairly steady in the first part of the year but then began to rise in the second half.
This graph shows how OPH changed during 2025.
The middle line shows the average OPH each week.
But the graph also has two extra lines, one above and one below.
These are called confidence limits.
The confidence limits were worked out using only the first six months of the year.
That first half of the year was steady.
So the limits show what “normal” looked like during that steady time.
When we look at the second half of the year:
- The OPH line rises.
- It moves above the upper confidence limit.
- It stays above it for quite a while.
That tells us:
This rise is probably not just random movement.
It suggests that something actually changed in the market around July.
Using a method called breakpoint analysis, we can see that the increase started in early July 2025. The year can be split into two parts: a steady first half and a rising second half.
Does This Happen in All Types of Races?
Odds on favourites can affect OPH. But when we compare races with odds on favourites and races without odds on favourites, the same upward trend appears.
When we compare UK racing with Ireland, something interesting appears. In the UK, OPH rises in the second half of the year. In Ireland, OPH stays mostly stable. This suggests the change is mainly a UK effect.
Why Does This Matter?
Overround and OPH do not directly tell us how much money bettors lose or how much bookmakers make.
But in general, the higher the OPH, the harder it is for bettors to make a profit.
We do not know exactly how much money is settled at Starting Price, or SP, in UK racing. However, the Tote uses SP for its guarantee and bookmakers also use SP. So it is reasonable to think that around one billion pounds could be settled at SP each year. This is likely a cautious estimate.
If the average field size is eight horses and OPH rises by about 0.15 percent per horse, then the total increase per race is about 1.2 percent.
1.2 percent of one billion pounds equals twelve million pounds. That is a large amount of money that may no longer be going back to bettors.
Does the Change Affect All Prices?
The increase is not the same at all odds.
Horses priced up to about 9 to 2 are mostly unaffected. Horses priced between 5 to 1 and 16 to 1 give worse returns to bettors. Very long shots give slightly better returns later in the year.
So the impact depends on what kind of prices a bettor prefers.
We do not know why bookmakers may have made this change. One possible reason is that they may be trying to reduce the cost of Each Way bets.
Why Only in the UK?
The rise only appears in UK racing. It does not appear in Ireland.
We cannot say for sure why this happened, or why it started in July. Possible reasons might include tax changes, new regulations, or market pressures. But we do not have proof.
Conclusion
In 2025, OPH did not stay the same throughout the year. It rose clearly in the second half.
When OPH rises, it becomes harder for bettors to win money.
If this trend continues, it may discourage people from betting on horse racing. They may choose to bet on other sports where they feel they get better value.
Steve Tilley March 2026