Base Rates: How often do Derby & Preakness winners nail the Triple Crown?

Two coinciding events …

In my Strategic Business Analytics course, we’re dealing with “base rates” — the likelihood of something occurring given prior results in relatively similar situations.

And,  a couple of weeks ago, Triple Crown winner American Pharoah won the Breeder’s Cup.

So, I thought it would be a good time to flashback to last May, when American Pharoah was heading into the Belmont as the odds-on favorite to win the Triple Crown … a case study in base rates.

Originally posted May, 2014

On Saturday, American Pharoah will try to win the Belmont — capping off his Derby & Preakness wins to capture the oft-elusive Triple Crown.

Based on Triple Crown history, what are his chances?

The simple – but very deceiving answer is 35%.

31 horses have won both the Kentucky Derby & the Preakness …

11 of them have won the Belmont and the Triple Crown.

35% … about 1 out of 3.

That’s not bad, right?


Let’s slice the numbers a little finer …


Prior to 1950, 9 horses won the Derby and Preakness … 8 of them won the Belmont and the Triple Crown.

That’s almost 90%.

Between 1950 and 1979, 10 horses won the Derby and Preakness … 3 of them won the Belmont and the Triple Crown.

That’s 30%.

Affirmed won the Triple Crown in 1978.

Spectacular Bid lost his shot at the Crown in 1979.

He was the first of a string of dozen horses to lose the Belmont with a shot at the Triple Crown .

To recap: chances of winning – based strictly on history – has dropped from near certainty to long, long-shot.


Some experts say that horses are now trained for specific distances, so the longer Belmont is a stretch for some horses that are tuned to the shorter Derby and Preakness distances.

Others say that horses that are trained hard for the first 2 legs of the Crown are just worn out when they get to the Belmont.

Still others point to the luck factor … that at least a couple of horses are near parity and a stumble or fast start can make a determining difference.

Despite the above, American Pharoah will likely leave the starting gate at an odds on favorite to win the Belmont and the Triple Crown … just like the prior 12 horses who failed in their bids.


Note that in 2009, Big Brown left the gates with bettors thinking he had a 76.9% chance of winning.

Big Brown finished dead last.

Good luck, AP



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