Best Odds Guaranteed

The Question

A lot of bookmakers offer what is called BOG or Best Odds Guaranteed. It means if you take an Early Price (EP) on a horse and the Starting Price (SP) is greater than the price you took, then you are payed at the better odds. Grammatically, it should be marketed as "BETTER" Odds Guaranteed and not "BEST" Odds Guaranteed but let's ignore that and investigate if this offer gives value to the punter and how much value.

The Data

I have been collecting price data on and off for horse races over the past year. The result is that I have a set of data for prices on all horses at different times of the day for a subset of all races ran last year. I have filtered this data to find the price available on Bet365 for each horse where I have recorded a price between the hours of 10am and 11am.  Since this data was collected ad hoc I don't have data for every horse, but the horses where I do have data, the data is accurate.

I have collected a second set of data from the Time Form website, this set of data gives me all Industry SP's and Exchange SP's and non runner information for all horses ran from Jan 2018 to Dec 2018. The total set is for 92,391 horses run.

I can mash both sets of data together. I filter out any race which has a non runner because a Rule 4 would have to be applied to the Early Price and I do not have enough information to calculate what the Rule 4 would be. I have also filtered out data where I do not have Early Prices recorded. It has left me with 5,969 horses where I have the Early Price, the Starting Price (which is all I need to calculate the BOG Price) and no Rule 4's.

This is not a huge sample but it is what I have and I think it shows the point.

The Results

Firstly you can see most of the Early Prices moved, with only 14% staying the same by SP. Notice that 42% of the time the BOG Price is better than the Early Price.

Price movements from EP to SP

How much better? The average Early Price was 21.49 in decimal (just over 20/1). The average BOG Price gave you a 15% up lift to 24.89 in decimal (almost 24/1). This looks promising until you consider the average Betfair Starting Price is 61.13 (or over 60/1) for the same set of horses.  

The Betfair SP is based on the betfair exchange which often produces a much higher price than the Industry Starting Price because of lower margins and overrounds. The difference is especially conspicuous in the long price horses. It has become the standard of what the "fair" odds are. If the BOG prices are giving us 24/1 and Betfair SP is 60/1 then even with BOG the bookie prices are falling way below "fair" value.

Let's not lose heart yet though, it's likely just the outsider bias that is skewing the average BOG Price. So break it down by Early Price odds. 

The table below shows that for some prices (highlighted) the Average BOG Price beat the Betfair SP, but only by a small margin and based on a small sample size.  The table also shows that for the long shot horses like the 100/1's the Betfair SP has averaged 456.92, that is FOUR times the returns by betting at Betfair SP.

Early Price	Avg BOG Price	Avg BF SP	Ratio BFSP/BOG	Count
1.62	1.68	1.60	0.96	10
1.67	1.67	1.63	0.98	11
1.73	1.87	1.93	1.03	12
1.83	1.97	1.92	0.98	14
1.91	2.04	2.11	1.04	22
2.00	2.33	2.38	1.02	17
2.10	2.26	2.33	1.03	18
2.20	2.41	2.38	0.98	12
2.25	2.42	2.45	1.01	19
2.38	2.57	2.50	0.97	15
2.50	2.70	2.68	0.99	28
2.63	3.08	3.23	1.05	35
2.75	3.04	3.18	1.05	53
2.88	3.23	3.50	1.09	27
3.00	3.36	3.54	1.05	68
3.25	3.66	3.81	1.04	70
3.50	3.83	3.95	1.03	89
3.75	4.40	4.75	1.08	113
4.00	4.79	5.08	1.06	134
4.33	5.06	5.41	1.07	62
4.50	5.09	5.43	1.07	149
5.00	5.96	6.75	1.13	217
5.50	6.76	7.49	1.11	191
6.00	7.13	7.60	1.07	169
6.50	7.57	7.95	1.05	143
7.00	8.30	9.38	1.13	193
7.50	8.71	9.54	1.09	106
8.00	9.76	11.33	1.16	210
8.50	10.77	13.69	1.27	89
9.00	10.87	12.55	1.15	239
9.50	11.52	13.89	1.21	25
10.00	12.14	14.55	1.20	218
11.00	13.03	15.67	1.20	258
12.00	14.51	18.29	1.26	177
13.00	16.25	21.32	1.31	271
15.00	18.33	24.51	1.34	268
17.00	21.13	28.74	1.36	291
19.00	23.32	32.15	1.38	92
21.00	26.19	41.26	1.58	286
23.00	27.16	42.52	1.57	81
26.00	31.45	54.42	1.73	264
29.00	34.69	61.28	1.77	86
34.00	41.14	82.93	2.02	261
41.00	49.49	114.45	2.31	145
51.00	59.66	148.34	2.49	164
67.00	76.19	230.24	3.02	173
81.00	96.40	347.61	3.61	50
101.00	111.23	456.92	4.11	154
126.00	134.33	558.94	4.16	18
151.00	156.83	678.48	4.33	60
201.00	203.78	763.34	3.75	36

The Conclusion

Backing at bookie prices, even taking BOG into consideration is usually less value than betting at the betfair price.  In general you will lose money betting at those prices.

Below shows your profit for betting on all the horses in my sample based on both BOG Price and Early Price without BOG. It shows that betting £1 on every horse in the 5,969 would leave you £1,057.48 down, and even with BOG you are still down but only by £516.77.

Early Price vs BOG Price losses over time

We can do better as we know the long prices are less value to begin.  If we bet only on the short favourites (<=2.5 decimal, 6/4 fractional) then it is about break even with the benefit of BOG. Between 6/4 and 10/1 is a small loss and backing everything over 10/1 would result in a huge loss even including BOG Prices.  Most people like to bet favourites any way, but most people don't like to bet as early as 10am, so it will be unlikely in my opinion that many punters will be getting enough benefit from BOG to turn their losses into even break even.

BOG prices split by banded odds P/L over time