The longer the odds on a horse running in the Grand National steeplechase, the less likely it is to complete the course, scientists have confirmed.
The findings show bookmakers know what they're talking about
That is one finding of a statistical analysis of outcomes of the annual, world-famous horse race at Aintree, UK.
The type of ground, the number of runners and whether the horse had run in the race before all influenced how many horses finished the course.
Details of the research are published in the scientific journal Nature.
A team from the University of Liverpool's faculty of veterinary science looked at 15 years' worth of Grand National results, a data set comprising 560 starts.
The results would seem to suggest that the bookmakers frequently get it right. The researchers used a formula called the starting-price multiplier - the inverse of the starting price - as a measure of the odds on a horse for simplicity.
A spokeswoman for bookmaker William Hill said odds compilers do not use a specific formula to work out odds on a horse.
They are partly based on opinion, including the balance between horses in a race.
The research is part of a wider project to look at improving safety for the racehorses involved in racing.
The University of Liverpool scientists also found horses that had never raced on the Aintree course were twice as likely not to complete the Grand National.
Dr Christopher Proudman, who led the research, told BBC News Online: "It's one of those things that when it comes out people say: 'Well that's obvious'. But I don't think people realised just how important it was."
A spokesman for Aintree Race Course told BBC News Online: "Is there a correlation between experience and falling? There obviously is.
"Hence the standard to enter and to run has been raised. Most of the safeguards are now in place at Aintree."
The spokesman added that every horse entered in the race was judged on its form by a panel of experts and subjected to a full veterinary examination.
Co-author Dr Peter Clegg said the study might have implications for horse intelligence.
"There is some form of memory there (in the horse). But that whole area is poorly understood and needs more research," he added.
Two other factors were also found to be associated with increased rates of non-completion of the race by horses: a large number of runners in the race and unusually hard or unusually soft ground.
Only 18% of runners will complete when the "going" is hard or soft, the study predicts.
Certain fences in the race also conferred a significantly increased risk of falling: the famous Becher's Brook, several open ditch fences, Canal Turn and The Chair.
The Grand National steeplechase comprises 30 obstacles over 7.2km (4.5 miles) and is watched annually by 600 million people worldwide.
This year's event takes place on 3 April.