How Predictive is the TDN 'Rising Star'?
From time to time the industry publication the Thoroughbred Daily News will make a young horse a 'TDN Rising Star', indicating that according to their opinion, the horse is one with considerable upside.
I decided to take a look at the awarding of this status and see if it had any bias, was truly predictive of subsequent performance, or if the status had no merit at all. From the TDN web site I got a hold of the 'Rising Stars' that were assigned between th
e 1st of January 2013 and the 31st of December 2014. There were 140 horses that were assigned TDN Rising Star status in the period and they were sired by 70 different stallions.
First, I wanted to take a look to see if there were any obvious biases in the data. I started by looking at the correlation between the number of TDN Rising Stars awarded, and during the same period of time, the actual performance of the sires of these horses as defined by graded stakes winners. The two variables - number of Graded or Group Stakes Winners and number of TDN Rising Stars - were moderately correlated at 0.445. Of course correlation doesn't mean causation, so just because a stallion has a lot of graded stakes winners doesn't mean he will sire a lot of TDN Rising stars, and vice versa, but there is still a moderate correlation between the two to investigate.
I created a linear regression model with the data, between the variable "TDN Rising Star count," a count of the number of horses awarded TDN Rising Star Status per stallion, and the 'number of runners' and 'number of GSW' in the same two year period that the sire had. The best fit model to predict the number of TDN Rising Star's that a stallion should have is:
Predicted Rising Stars = 1.20975 -0.00017*(# of Runners) + 0.098651*(# of GSW)
In baseball, they have what is known as 'wins above expectation'. That is, how many wins does a team have above the number they are expected to achieve? Using a similar metric here, I looked at the 'Rising Stars: above or below expectation? The question being, how many Rising Stars were awarded to a stallion compared to expectation given the number of runners that the stallion had and number of graded stakes winners in the same period.
First let's take a look at the list of stallions that should have had more TDN Rising Stars.
What you can see from the above chart is that there are a number of stallions that should have got a few more TDN Rising Star's that they did, given the number of GSW that they sired in the same period. Darley Stud stallion Dubawi as an example, had two TDN Rising Star's in the period where the expectation was that he should have got at least four, maybe five. Indeed the stallions that were under-represented in terms of awarding TDN status were very Euro-centric which is probably a commentary on the overall US bias that the daily has. I'm not saying that is right or wrong to have that bias, just that it exists.
What if we look at the stallions that were over-represented and should have had less TDN Rising Stars?
There were quite a few more stallions who got more Rising Star's that they should at face value. I'll let you try to discern the reasons why. There were five stallions that should have had more Rising Stars, given their performance in the period and another nine that got more than they probably should, the other 56 stallions had the number of Rising Stars at a rate that you would expect them to have received.
What about the performance of the Rising Stars themselves? 103 of the 140 (74%) of the Rising Star's were assigned a Rising Star status off their maiden win. Of the 103, 34 of these, or a third, have gone on to win at Graded Stakes level. Sixteen of those 34 have won at G1 level. On these two metrics alone - 34% GSW and 16% G1SW - the TDN Rising Star status, off maiden wins alone, is a reasonably strong predictor of long term racetrack success.
However, what of the 37 that were given Rising Star status off allowance/conditions or Listed stakes wins? Eighteen of the 37 (49%) became Graded/Group stakes winners and 7, or 19% have become G1 winners. The group where there is more information to discern racing quality has a slightly higher percentage that become a superior runner.
What about our group of sires whose progeny were being over-represented by Rising Star's relative to their production of superior runners generally?
Considering the data above, you could probably look at Tapit and agree that while he has received a lot more Rising Star's than he should have based on his performance at stud, they have turned into good horses following being awarded the status. Of the seven that were given Rising Star status off their maiden win, three have gone on to be GSW and two of these G1SW. For the rest of the stallions, the Rising Star status looks somewhat misplaced, especially Medaglia d'Oro. In fact if you go back to when they started the 'TDN Rising Star', 13 horses by Medaglia d'Oro have been assigned Rising Star status but only three - Vancouver, Gold Medal Dancer and Al Zir - have achieved a win at graded/group level. Medaglia d'Oro is a very good sire, but whomever is selecting them to be TDN Rising stars is both picking too many of them, and the wrong ones.