How accurate are the odds quoted by bookmakers? © Getty Images

How accurate are the odds quoted by bookmakers?

Here we work out how accurately bookies' estimated odds reflect the true probability of an event happening.

Asked by: Anonymous

Advertisement

Bookmakers’ odds give an estimate of the probability of, say, a horse winning a particular race. And if they were reliable, around 50 per cent of horses with even odds would win their races, around 33 per cent of those with odds of 2-1, and so on, right down to just 1 per cent of ‘long shots’ with odds of 100-1. According to leading gambling expert Professor Leighton Vaughan Williams of the Betting Research Unit at Nottingham Trent University, comparisons with actual results show that odds shorter than around 2-1 do tend to be reasonably accurate. However, bets placed at longer odds – say, 14-1 or worse – become progressively unreliable, with the real chances of winning being much lower than the odds suggest.


Advertisement

Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.