Understanding the Starting Price (SP) and Betfair SP (BSP) in Horse Racing
When you place a bet on a horse race, you’ll often see the option to take the Starting Price — commonly abbreviated as SP. It’s a term with deep roots in the sport and has evolved dramatically in the digital age, especially since the arrival of the Betfair Exchange and the creation of the Betfair Starting Price (BSP).
In this post, we’ll explore the origins of the SP, how it was used on course, how Betfair’s BSP works, and why it’s not as straightforward as many bettors believe — particularly when it comes to testing betting strategies.
The Historical Origins of the Starting Price (SP)
The Starting Price dates back to the 19th century, when most betting took place on course at race meetings. Bookmakers would shout their odds across the betting ring, competing with one another for business. Just before the race began, odds would settle into a general consensus — the starting price.
In essence, the SP was designed to be a fair reflection of the average odds available on course at the moment the race started. It provided a standardised price that off-course bookmakers could use to settle bets placed elsewhere (for example, in betting shops or via telephone).
Before computerisation, official SP reporters would stand trackside, noting odds from multiple bookmakers and submitting the most representative prices to a central compiler. That figure became the official SP recorded for the race.
Why Bettors Choose to Bet at SP
Betting at the starting price offered simplicity and reassurance.
If you didn’t want to worry about fluctuating odds before the off, taking SP meant your bet would be settled at the industry’s final agreed price. It was particularly useful for ante-post or multiple bets, where you couldn’t always be certain when or where you’d get the best value.
Even today, traditional bookmakers still settle many bets at SP — especially when no fixed odds are available or if the bettor prefers not to take a price early.
The Birth of Betfair SP (BSP)
When Betfair launched its Exchange in 2000, it revolutionised how odds were determined. Instead of taking prices from a bookmaker, users could set their own by backing or laying horses against one another.
But there was still a gap: what if you wanted a starting price equivalent on the Exchange?
That’s where the Betfair Starting Price (BSP) came in, introduced in 2007. It aimed to replicate the old SP system — but derived from the balance of back and lay orders on Betfair at the off.
How BSP Is Calculated
The BSP isn’t an average or a midpoint — it’s the price at which all unmatched backers and layers can be matched at the moment Betfair suspends the market for the start of the race.
In practical terms:
- All unmatched back and lay bets marked “At SP” go into a pool.
- Betfair’s algorithm finds the price that allows the maximum amount of money to be matched between the two sides.
- Any remaining unmatched exposure is settled at that derived price.
It’s a clever system that allows users to bet at a fair market-driven price without taking fixed odds, and it has become hugely popular with both casual bettors and data-driven traders.
Why the Betfair SP (BSP) Isn’t What It Seems
While the BSP is often described as the Exchange’s equivalent of the old SP, there’s a critical difference — and one that has big implications for anyone using BSP data to test or model betting strategies.
On Betfair, markets are suspended at the official off time, but in practice this happens a few seconds after the race has actually started.
That delay is crucial. During those few seconds, the market continues to trade, and people are still placing and cancelling bets — often using automation or in-play tools.
This means the BSP is calculated using data that includes bets placed after the race has begun, not before. In other words, BSP reflects the market as the race starts, not just before it starts.
So if a horse breaks well from the stalls or stumbles slightly, those early in-play reactions can already influence the final BSP.
The Problem for Strategy Testing
This timing issue creates a major flaw for anyone back-testing betting systems using BSP data.
If you model a strategy assuming you could have backed a horse at the BSP before the race, you’re working with an unrealistic scenario. In real life, you can’t know or lock in that BSP beforehand, because it only becomes known afterthe market is suspended.
That means any historical edge found using BSP prices may not be reproducible in live trading. What appears profitable on paper could fail in real-world conditions — simply because the BSP is influenced by activity that occurs after the race has started.
Final Thoughts
The Starting Price has come a long way from the betting rings of yesteryear to the digital pools of the Betfair Exchange. While BSP provides transparency and a market-driven alternative to traditional SPs, it’s not a perfect analogue.
For traders and bettors who rely on data, understanding this timing nuance is essential. The Betfair SP may look like a clean, objective number — but in truth, it’s a reflection of the market a few seconds into the race, not before it.
So if you’re building or testing a strategy, remember: the BSP is not the same as a pre-race price, and using it uncritically can lead to misleading results.