What proportion of favourites win?

Across the whole of horse racing, the fact that, on average, approximately one-third of favourites win or, conversely, approximately two-thirds of favourites lose, is well chronicled. However, the proportion of winning favourites varies widely according to the type of race being contested, the number of runners, the odds on offer and so on.

For example, it stands to reason that non-handicap races should produce a higher proportion of winning favourites than handicap races, in which every horse, theoretically, has an equal chance of winning; in fact, in non-handicap races, approximately two-fifths, or 40%, of favourites win. Similarly, it might be expected that the proportion of winning favourites is inversely proportional to the odds on offer and this is, in fact, the case; less than 23% of favourites sent off at 2/1 or longer win, but 45% of those starting at 15/8 or shorter do so, as do 86% of those starting at prohibitive odds of 1/4 or shorter.