Betting statistics from the 2008-2009 season
This is the first season review that I have been able to post since 2006-07. Unfortunately my 2007-08 campaign ended prematurely when I had a serious acccident while riding my road bike. The accident occurred on Christmas eve 2007, and I was forced to spend the next six months in hospital and rehab.
I have placed on this site two Excel files. Both are in Excel tab-delimited text format, so they should be readable by any version of Excel. If any file launches the Excel Wizard, simply follow the instructions.
The first Excel file contains my personal Betfair results for the period November 2008-March 2009 inclusive. They represent a level stake win bet on every horse in the top two that was offered on Betfair at equal to or greater than the V-30 odds, with the stakes normalised to 1 point per matched bet.
A summary of the results obtained reads as follows:
Total bets matched
1367
Number of winners
143
Strike rate
10.46%
Gross profit
5.13
Average profit
8.60
Percentage gross profit
0.38%
Average level matched
12.58
Average level winners
9.60
Sum profit before losers
1229.13
Betfair commission
60.23
Net profit
-55.10
The spreadsheet shows a good profit for November 2009 followed by a series of roughly break-even months in December and January.
February and March show an alarming decline, so alarming in fact that I was forced into a complete re-think.
This was not just a case of blind panic. The rolling ARCHIE scores (read Steve Tilley's excellent article) were telling me that something had gone seriously awry. The fact that the accumulated losses were due for the most part to Betfair's commission at 4.9% was small consolation.
I came to the conclusion that the arbitrary cut, limiting bets to horses in the top-two rated, was doing more harm than good. I was saved from total catastrophe by the fact that I always operate with a generous bank, and trigger a stop-loss option when the total of losses incurred approaches 50% of my bank.
As I've pointed out before, HOOF ratings
are in essence a stats-based odds-line. It is a characteristic of most
odds-lines that the value to be found in a race is not assigned to one
stand-out value horse. It tends to be distributed amongst a number of potential
candidates. Here is an example from a typical small race:
The V_30 column represents the value odds with a theoretical 30% advantage
to the backer. The V_PLUS column represents exceptional value
at 40% or more in favour of the backer.
Worcester:4.20 Handicap hurdle:8 rnrs
HORSE
TR-PROB TR-ODDS V-30 V-PLUS
Two Miles West
0.234 10-3 11-2 7-1
no match at 11/2 or better
Olmeto Collonges
0.126 7-1 11-1 14-1
no match at 11/1 or better
Mith Hill
0.125 7-1 11-1 14-1
no match at 11/1 or better
Bob Mountain
0.124 15-2 11-1 16-1
matched at 12/1 = lost
Chinara
0.104 9-1 14-1 18-1
matched at 28/1 = won
Raslan
0.098 10-1 14-1 20-1
matched at 14/1 = lost
Little Shilling
0.094 10-1 16-1 20-1
no match at 16/1 or better
Quattrocento
0.09 11-1 16-1 22-1
no match at 16/1 or better
However, old betting habits die hard, and I have always been reluctant to bet on more than one, or at the most two, in a given race. My re-think at the end of March involved a retreat from that strategy.
And so to the second Excel file. This shows the results for a 'bottom fishing' expedition that involved betting on every V-30 horse in all-aged handicaps regardless of rank order. A breakdown of the results obtained reads as follows:
Total
matched bets
956
Winners
54
Expected winners
30
Strike rate for matched bets
5.65%
Gross profit to 2 GBP
702.50
Total winnings before losses to 2
GBP 2503.28
Average profit per win to 2 GBP
46.36
Total staked to 2 GBP
1908.78
Percentage gross profit
36.80%
Average level matched
31.86
Average level winners
24.18
Average level winners @ sp
15.01
Betfair advantage over sp
9.16
% Betfair advantage over sp
37.90%
Average level winners @ best board
price 16.66
Betfair advantage over best board
price 7.52
% Betfair advantage over best board
price 31.09%
Betfair commission to 2 GBP
@ 4.9% 122.66
Betfair commission as percentage of
gross 17.46%
Net profit to 2 GBP
579.84
Number of races
215
Average level stake liability per
race 4.45
Average liability per race to 2 GBP
8.89
Winning race strike rate
25.12%
Current ARCHIE score
19.81
My stake was, of necessity, the minimum. I averaged around 4.5 matched bets per race. In some races I had up to nine matched bets running for me, but after a while, I got used to the idea of an average liability per race of 4.5. I came to the conclusion that it was no worse a position to be in than if I had laid a 7/2 shot.
The campaign lasted from 11th April until 24th May when the motherboard on my Mac failed and I was forced to call a halt. I'll let the results speak for themselves, but please note that they are subject to the following caveats:
1. LIQUIDITY The sums that I was placing
were the minimum allowable on Betfair.
In many cases, it is highly unlikely that
one could have obtained a full or
even a partial match if one had scaled
up the stake. Unless the
betting is very strong, I doubt whether
there is much scope for a thick
bet at the extreme back end of the market.
2. TIME OF YEAR It has always struck me
how certain times of the year
favour a rash of shock results. April
is a classic case given
frequent changes in the going, and additionally,
the change from winter
to summer racing. Whether the results
I obtained are repeatable at
other times of the year remains to be
seen. May, though profitable,
was more difficult, with a noticeable
decline in liquidity.
Incidentally, I think that the relative
lack of liquidity during the
summer months when the flat is in full
swing, makes it unlikely that a
summer campaign will ever prove to be
worthwhile.
3. LUCK IN GETTING MATCHED I decided quite
early on to put my bids in
only when the market conditions were optimal
- preferably more than 25k
staked and an over-round not greater than
102%. This generally meant
getting on around an hour and a half before
the start of the first race
at any given meeting. On those terms I
made a number of great matches,
some of which were clearly the best that
the market had to offer.
4. THE BETFAIR ADVANTAGE OVER SP It's worth
noting that the gross
percentage profit is not far off the Betfair
percentage advantage over
sp. At sp, I'd have broken even at best.
In fact, given that many of
my successes were less than the required
V-30 at sp, it's likely that
I'd have made a loss.
5. RACE TYPE In opting for all-aged handicaps
I chose well. I doubt
if the results could be repeated in novice
events.
6. ARE THE RESULTS REPEATABLE? I
have no idea. Trying to look
back from 11th April in order to work
out what might have have been
over the course of a whole season, is
virtually impossible, since the
Betfair prices that were obtainable are
unknown. The only hard evidence
is the Betfair sp. On that basis,
there is evidence that seems to indicate
that the the season as a whole was, in
fact, profitable. However, since
the Betfair sp data are a relatively recent
innovation, there are no plausible
results for seasons prior to 2008-09.
On the plus side, the results are not backfitted,
the ARCHIE score is
reassuringly high, and the results do
not include at least three winners
at huge prices that went in at the Aintree
Grand National meeting. In
addition, around half of the winners that
were matched at the required
V-30 price on Betfair, were 'under the
radar' in the sense that they did
not qualify either at sp or at best board
prices.
PERFORMANCE OF THE RATINGS COMPARED WITH THE ON-COURSE BETTING MARKET
It is generally accepted that the betting market at the off is pretty efficient, in the sense that starting prices are the most accurate predictor of a horse's chance of winning. That they do not perfectly represent a horse's chance of winning is a reflection of the bookmakers' take out, or percentage, also known as the over-round. Thus, 6-4 shots don't win exactly 40% of all races, but more like 37%. It is also the case that the longer the odds, the greater the bookmakers' take-out. Thus 20/1 shots should, in theory, have a strike-rate of 4.76%. In practice, it is more like 3%. In other words, the true odds about a 6/4 shot are around 13/8, and the true odds about a 20/1 shot are closer to 33/1. This is why bookmakers prefer to see outsiders win.
Consider the table below.
ODDS RANGE
MARKET PROBABILITY HOOF
'TRUE PROBABILITY'
2008-09
Odds-on
0.58
0.66
EV to 11/8
0.43
0.43
6/4 to 15/8
0.35
0.35
2/1 to 11/4
0.27
0.30
3/1 to 4/1
0.20
0.20
9/2 to 6/1
0.14
0.15
13/2 to 8/1
0.10
0.12
9/1 to 12/1
0.07
0.10
14/1 to 20/1
0.04
0.06
22/1 to 40/1
0.02
0.04
50/1 to 100/1
0.005
0.02
> 100/1
0.0002
0.005
The table tells us, inter alia, that at the front end of the market, the predictive power of the starting price and the HOOF 'true probability' rating are virtually the same. Thus horses in the betting market range of 6/4 to 15/8 have a win probability of 0.35, which is identical to that of horses in the same odds range assigned by the HOOF program. To put this another way, horses in the market odds range 6/4 to 15/8 win 35% of their races. This is identical to that of horses in the same HOOF 'true probability' range. (Actually, they ought to win just over 37% of their races, but they don't.)
If one looks beyond the front end of the market, we see that in the case of outsiders, the HOOF 'true probability' figure is a better predictor of a horse's true chance of winning than the market. For example, in the range 14/1 to 20/1, the strike-rate for horses priced by the betting market between 14/1 and 20/1 is 4%.(probability of 0.04). For the ratings it is 6% (probability of 0.06). In the range 22/1 to 40/1, the market scores 2% (probability of 0.02), while the ratings score 4% (probability of 0.04).
It is therefore unsurprising if the ratings
are best at finding value among the outsiders rather than at the front
end of the market. The downside of this, as I have frequently pointed
out, is a very low strike-rate, and the need for steady nerves and an enormous
bank.