More on Price Movement in NH Markets, Part 1

Back in October I wrote an article that examined some betting market data whereby I investigated patterns of price movement from early morning odds to SP in UK NH racing. I felt now was good time to revisit the idea but switch attention to movement between opening show and SP.

This is first of a two-parter with data taken from the last five full years covering 2020 to 2024. I have used William Hill bookmaker prices and, for the remainder of this article, I will use ‘OS’ to stand for the Opening Show Odds.

As I mentioned in earlier work, the OS for most races occurs around 10-15 minutes before the race is due to start. Each horse will have its opening price and then, as money is wagered in the period before the race starts, the prices will begin to fluctuate. Some will go up, some down, some will end up the same price as they started. Price changes are also driven by what happens on the betting exchanges.

As I did for the previous research let me start by sharing the figures for all runners over this time frame to see what percentage shortened in price, lengthened in price (often known as drifting), or stayed the same when comparing their OS to their final Starting Price Odds (SP).

These percentage splits are very close to those I found for flat racing with far more horses lengthening / drifting in price than shortening in price. Once again, the smallest percentage figure occurred with horses staying the same price.

Market movement during this short period before the start of the race is a good indicator of a horse's chance of winning as the graph below shows when we examine the win strike rates of the three groups:

Horses that shorten in price have won more frequently, edging towards twice as often as those that drift. In terms of returns, to Industry SP horses that have lengthened in price (drifters) would have lost you a hefty 30p in the £, while those that have shortened in price would have lost you around 15p in the £. To BSP the gap is much reduced with an 8.6% loss for drifters and a 5.6% loss for ‘shorteners’.

Let me now share the yearly percentage of runners splits for the three groups in terms of comparing their OS odds to their SP odds:

As we might have hoped the splits have been similar year on year. Readers may notice that 2020 is slightly out of kilter, but my guess is that Covid was a key reason behind this. No spectators at racecourses for around eight months in 2020 meant we had an unusual situation come Opening Show with no oncourse bookmakers taking money. It is also the case that, since Covid and 2020, the starting price is framed more significantly around off-course liabilities than on-course, reflecting where the majority of betting action happens nowadays.

For the next part of this piece, I would like to focus on the percentage of horses that lengthened / drifted in price showing a course-by-course comparison. The courses are ordered highest percentage to lowest. As a reminder, the overall figure for all courses was 46.5%:

I have highlighted in red those courses that had the smallest percentage of drifters and what immediately stands out is that these tracks are universally considered to be top tracks. In fact, if we look at the list of courses that have held the most Graded races over the past five seasons we see the following:

These same seven courses showed the lowest percentages for drifters. I suspect there are two main reasons for this. Firstly, stronger markets exist at these courses – more money is wagered (off course, on the exchanges, and on course); and, secondly, there tends to be better overall knowledge of the horses that race at these tracks due to the average class level, making early markets more efficient / accurate.

Thinking about class of race, based on my second theory noted above, we might hope that if we look at the percentage of runner splits within each class, the higher classes of race would see a smaller gap between horses that shorten in price from OS to SP compared with those that lengthen/drift.

I have lumped Class 6 races in with Class 5 purely because there are very few Class 6 races in National Hunt racing. In addition, I have added an extra column which shows the percentage difference between horses that have shortened compared with those that have drifted. Here are my findings:

As hoped, the theory has held, with the highest class of race (Class 1) seeing by far the smallest gap between shorteners and drifters of 5.3%. As can be seen, once we get to Class 4, the gap extends to 16.7% for Class 4 races and 14.9% for Class 5/6 races. Hence, for those of us who may still take a bookmaker’s price between OS and the start of the race, the stats for Race Class and the previous course ones should help inform us more accurately about the chance of our selection drifting or shortening in the ten minutes or so before the race. For punters, having the overall stats gives us a good 'feel', but breaking things down into subcategories can offer more knowledge and understanding of how prices may move.

My focus now is to look at price movement from Opening Show to SP within different price bands. The figures are split by percentage of qualifying runners:

These price bands are based on huge sample sizes so we can be confident that these types of figures are likely to be replicated in the future. Possibly the most eye-catching percentages are those for bigger priced runners. Once we get to an Opening Show of 18/1 or more, over 50% of such runners have drifted in price. There also seems to be no difference to the overall norm when it comes to those priced up between 9/2 and 6/1. The percentages between shorteners and drifters are close to parity with a slight edge to shorteners. To see this more clearly let me graph the comparison:

The graph clearly shows this ‘close to parity’ situation with the 9/2 and 6/1 Opening Odds price band. Expanding this slightly, it also shows that the percentages are closest from 100/30 to 8/1 compared with everything else. We knew already that drifters occur more often than shorteners but seeing these price splits offers further appreciation of how likely a horse may be to shorten or drift. Looking back at the flat article I wrote we witnessed a similar pattern in terms of how the overall graph looks.

To conclude, understanding how a betting market may evolve from Opening Show to SP is an area that is rarely analysed. There are some parallel patterns with the flat findings I previously shared, as you might expect. In many ways this is a positive as it provides greater confidence that OS to SP prices will continue to move in similar ways in the next few years.

My next article will be a follow up to this one, and will look at some additional areas such as race type and trainers. Until then...

- DR

Other Recent Posts by This Author:

• Looking at Past Cheltenham Festival Trends
• Specific Course/Distance Analysis: Lingfield 1m2f
• More on Price Movement in NH Markets, Part 2
• ‘SR’ Ratings on the All-Weather
• When NH Trainers run two in the same race