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A.P. Indy and Stallion Ratings

The wins of Orb in the Kentucky Derby (gr. I) and Princess of Sylmar in the Kentucky Oaks (gr. I) further solidified the pensioned Lane's End stallion A.P. Indy as the premier sire line source of classic speed in the North American Thoroughbred. Indeed, with Normandy Invasion (by Tapit (TrueNicks,SRO)), Dreaming of Julia, and Revolutionary (out of an A.P. Indy mare) all running well in their respective races, one can see that in years to come inbreeding to A.P. Indy could easily become as prominent a method of upgrading for classic speed as inbreeding to Mr. Prospector is today.

The Kentucky Derby in particular did also throw an interesting light on how we as an industry rate a stallion's performance at stud. The win of Orb firmly placed his sire, the Spendthrift stallion Malibu Moon (TrueNicks,SRO), among the highest echelon of horses standing at stud today. Indeed, the day after the Derby, Craig Bernick of Glen Hill Farm tweeted the following:

What Craig alluded to in his tweet, and what we at TrueNicks are very aware of, is the measure of opportunity. The TrueNicks algorithm itself is built on a proper assessment of opportunity in order to gauge just how well the mating at hand is performing. When it comes to stallions, however, how well do we measure opportunity? For those not familiar with the terminology, here is a rundown of the more prominent measures of stallions in the industry.

Average Earnings Index (AEI): indicates how much purse money the progeny of one sire has earned, on average, in relation to the average earnings of all runners in the same years. The average earnings of all runners in any year is represented by an index of 1.00, so a stallion with an AEI of 2.00 is twice the average, etc.

Comparable Index (CI): indicates the average earnings of progeny produced from mares bred to one sire when these same mares were bred to all other sires. Only 32% of all sires have a lifetime AEI higher than their mares' CI, and the comparison of the two is an often-used measure of stallion performance.

Annual Progeny Earnings Index (APEX): a series of indexes developed by Bill Oppenheim. The signature index, which is called the "A Runner Index", began life as an attempt to modify the impact of one huge earner on a sire's cumulative AEI. It does this by measuring the frequency with which a sire's runners reach the top two percent of earners, each year. The calculations and analyses are restricted to the last seven years. By his own admission, Bill does this because he doesn't want to let once-great stallions live entirely on past glories.

So lets take a look at A.P. Indy and his sire line with these figures.

Sire Foals of
Racing Age
"A Runner" (2012)
A.P. Indy 1,224 4.03 2.90 3.24 -12%
Bernardini 630 3.16 1.84 3.12 -70%
Congrats 296 1.31 1.50 1.61 -7%
Flatter 457 1.63 1.65 1.18 +28%
Jump Start 677 1.94 1.58 1.36 +14%
Lucky Pulpit 98 2.70 1.61 1.17 +27%
Majestic Warrior 249 n/a 1.37 1.43 -4%
Malibu Moon 1,053 2.18 1.80 1.68 +7%
Mineshaft 474 2.88 2.13 2.21 -4%
Pulpit 861 2.25 1.90 2.51 -32%
Sky Mesa 566 2.19 1.62 1.74 -7%
Stephen Got Even 650 1.03 1.42 1.41 +1%
Tapit 644 2.63 2.31 1.99 +14%

It shouldn't take readers of this blog long to work out a few problems with these numbers!

Let's start with the now-retired patriarch A.P. Indy. His APEX rating is one of the best in the world and he continues to produce outstanding runners, mainly over two turns in North America. His AEI is also high but it is less than his CI, indicating at face value, that he is degrading the mares that are bred to him! How is that possible? Well, here is where a problem with the CI is quickly exposed. This rating makes no allowance for the quality of the stallions that were bred to in creating the CI. In A.P. Indy's case, some of the mares that were bred to him had their best foals early in their career by other stallions and then were "upgraded" to A.P. Indy's book for a commercial mating. Additionally, mares that were often bred to A.P. Indy, and may have produced a superior runner by him, were also sent to other premier sires at the time who may have also sired a superior runner out of that mare. These types of commercial assortative matings is what fuels a high CI.

The fallacy of the AEI/CI comparison is magnified in the case of Bernardini (TrueNicks,SRO). Here is a young sire whose APEX and AEI ratings place him as a superior sire, but whose CI—a massive 3.12—would indicate that he is downgrading his mares (they are doing better with other stallions). In Bernardini's defense, as was the case with Mineshaft (TrueNicks,SRO) when he retired to stud, the mares that have generated this CI have been bred to sires where the runner that is creating the CI may well have been the best foal that the mare ever had prior to being bred to Bernardini. At a certain point it is almost impossible for a young stallion to jump over the CI created by his mates having previous success with quality stallions and be seen to be improving his mares—that is unless this CI is modified to reflect the quality of the stallions that created the CI in the first place.

If you haven't noticed already, the APEX rating doesn't have a comparable index so there is no way to tell if the stallion is in fact doing better or worse than the opportunity afforded to him using a comparative measure. The AEI/CI comparison does highlight the performances of Tapit, Flatter (TrueNicks,SRO), and Jump Start (TrueNicks,SRO) at stud, with all three of these stallions, in addition to Malibu Moon, "upgrading" the mares that were bred to them. So what then do we make of Lucky Pulpit (TrueNicks,SRO), standing at Harris Farms in California for just $2,500 this year? By both the APEX ratings and AEI/CI comparison, this son of Pulpit is an elite stallion, however his ratings may expose the issues with using earnings, as APEX and the AEI/CI do, to measure racing class. Lucky Pulpit, with a small number of foals of racing age, looks to be benefiting somewhat from the restricted California-bred purses, where his runners are able to earn significant funds in restricted racing and generate high APEX and AEI scores. That said, he still has to do it, so at some level the numbers show that Lucky Pulpit may well be an undervalued sire in California.

So we have established that in order to really measure a stallion's opportunity, a comparable index is required, but in order to make it valid, the biases of the quality of the stallions that generated the CI needs to be accounted for (and quite possibly the foal rank of the foal). This would establish the individual stallion's merit, but then what about comparing the ratings of one stallion to another?

Going right back to the work of Joseph Estes, the former editor of The Blood-Horse, creator of the AEI, and considered the doyen of statistical evaluation of stallions, the racing class of the racemare is paramount to the success not only of the mare at stud, but also the stallions that she is bred to. That is, on average, better class racemares will breed a better class runner, all other things being equal. This is why APEX rating comparisons such as between Malibu Moon (2.18) and Pulpit (2.25) are intellectually flawed. The racing quality of mare is significantly different between these two sires. While Pulpit received some good racemares in his first years at stud at Claiborne, Malibu Moon, as Craig Bernick indicated, received some very average racemares. Thus, the performance of Malibu Moon in comparison to other stallions is significantly better than his 2.18 would indicate, as the APEX rating makes no allowance for the racing class of the mares bred.

Taking out all the influences of both the racing class and the production class of the mares bred to a stallion would create a figure that would represent a true genetic improvement index for stallions. While this is yet to be achieved, it can be said at face value that, given the quality of mares that he has covered and their performance as both racehorses and producers, when compared to his peers Malibu Moon may well be, as Craig Bernick suggests, the best sire in North America.

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Very very nice article, very informative and very well explained. This is my favorite subject, thank you.

JorgeG 07 May 2013 10:48 AM

Wonderful horse; Malibu Moon. Even better article. My compliments. I'll keep a sharp eye on Majestic Warrior, now that he has a major winnner.

Gregg 07 May 2013 4:15 PM


Orb in the Derby and Princess of Sylmar in the Oaks represent a BREAKTHROUGH for the AP Indy sire line, not a solidifying of A.P. Indy as "the premier sire line source of classic speed in the North American Thoroughbred."  AP Indy has been a source of stamina no doubt but not for the 3YO classics. His progeny including those of his sons have been hyped for many years but failed to deliver. Take a look at the list of Kentucky Derby, Preakness and Belmont winners over the period that AP Indy was active as a sire and what you see is underachievement. Now there is a breakthrough and all of a sudden its the premier source of classic speed in North America ...give me a break. The AP Indy sire line has a far way to go to compete with the lines of Mr Prospector or his sire Raise A Native or his grandsire Native Dancer, as well as the Northern Dancer line in relation to being the source of classic speed (by classic speed I think you mean horses than effectively/successfully carry their speed over the classic distances). The AP Indy sire line have been notoriously late developers as 3YOs therfore lets put some proper perspective on the breakthrough.

Malibu Moon got off to a 'jack-rabbit' start in his stud career with Declan's Moon a few years back and has thrown some good ones, mostly fillies of which Devil May Care come readily to mind but he's not the best of the AP Indys. Tapit has produced Grade 1 quality more consistently and showed to propesity for the occassional special one IMO.      

Ranagulzion 07 May 2013 5:12 PM

Great article. I just adore all A.P. Indy line mares & stallions. He is truly one of the best sires around, and in my opinion is joining the ranks of such sire greats as Storm Cat & Mr. Prospector. -To name only a few names.

Lets all cross our fingers now that Orb can pull it out to win the TC!

Leila 07 May 2013 5:33 PM

Couldn't agree more. With all our tools of evaluation, none tells the true story of opportunity. I always use AP Indy as the best reason NOT to trust AEI/CI comparisons. And the two measures used by MW - one measuring racing performance, and the other production – while useful completely disregard the young highly-bred mare who didn't make a name on the track.

That is why after extensive sampling we at Darley have developed our own rating that evaluates the complete pedigree as well as other well known and less well known environmental factors that play a part in the outcome of a particular mating.

John Boyce 07 May 2013 6:04 PM


Not sure we are going to agree on this....Bernardini won the Preakness and Rags to Riches won the Belmont and the Oaks, with Secret Status winning the latter also. Derby winner Super Saver is out of an A.P. Indy mare as is Oaks winner Plum Pretty.  This is forgetting horses like Aptitude, Bodemeister, Ice Box, Nehro, Bluegrass Cat, etc (and I'm sure I am missing quite a few) with A.P Indy in three generations that performed well in the classic races.

Apart from Distorted Humor and maybe Unbridled, I’m not sure any individual stallion has been more represented in the pedigrees of placegetters in the American classic races past 15 years or so. As with a lot of sires his sire sons may have initially disappointed as sire sons but you also have to remember Mr Prospector did have Hello Gorgeous as one of his first sire-son representatives along with Fappiano.

Agree with you on Tapit though. He looks to be something special given opportunity, but then as flawed as the numbers are, they show that already.

Byron Rogers 07 May 2013 7:50 PM

I would think that the Russians were the first to recognize the worth of Malibu Moon..

Hal Dane. 08 May 2013 5:13 AM

Thanks for the solid analysis Byron, as always. I value the AEI/CI indices a lot, but are only one measure. The mare quality index has to be upgraded from a simple CI, if for no other reason that it deals only with runners, and a calculation of the percentage of runners from foals at least would help.  Also, in terms of a broodmare, it would be interesting to see if number of starts would also imply longevity/soundness and hence imply the long term soundness of the animal.  that of course is compromised by removal of the best mares from the pool who go immediately to the shed after quality G1 performances.

In terms of Derby winners, I think Fappiano is king and it may be true regarding general runners, placers in the classics as well. That the Fappiano line mares nick well with AP Indy would indicate that possibility of even stronger long term success in the classics for AP Indy.


Joltman 08 May 2013 9:38 AM

I'm so disappointed. I thought that I would find herein an expanded explanation of the a.e.i., which is hardly explained by the usual squib. If, as is customary, a sire has horses racing in various countries with varying purse structures, how is the a.e.i. calculated? Is there an international value? Are Japanese earnings, say, pro-rated? Is the a.e.i. individualized for this factor?

Cassandra.Says 08 May 2013 10:48 AM

The Comparable Index (CI) when compared with AEI is a particularly untrustworthy barometer for stallion performance when applied to elite-type stallions, especially those that went to stud with high reputations. These stallions generally receive the highest quality mates, many of whom are regarded as such due to their exceptional PAST produce records. Whille it is fairly common that some mares in the course of their production will produce an exceptional runner, or multiple high class runners-and these are the very mares so "cherry-picked"- it is extremely uncommon for these same mares to perpetuate that extreme degree of production performance-no matter their subsequent mate. As we have ever more evolved into a sales-oriented industry, this AEI/CI comparative has become all the less meaningful. The relevance, alone, of AEI is another matter, and it's undeniable that the elite stallions of the past, by and large, had higher AEIs. Just take a look at Bold Ruler's, and some others should you doubt this. This fact alone should telegraph the inherent shortcomings of AEI in stallion performance evaluation. There are probably several reasons for this apparent past vs present disparity ( better left for another time), and it's but one example of our mistake in relying on shortcuts vs intense study.      

sceptre 08 May 2013 11:24 AM


I agree. None are perfect but then it gets back to the concept of performance, it is not a single character/trait rather an amalgam of ability over certain distances, over certain ages, over certain tracks, etc.

Byron Rogers 08 May 2013 1:38 PM

Due to my mathematical background, I use the formula 2*AEI-CI to give a quick evaluation of sires index (SI).  What this does is to lower (or raise) the Sires index value (SI)by the difference between his AEI value and the mares CI.  Think of a graph with three columns:  (SI, AEI, CI) equally spaced.  A straight line from CI through AEI will produce SI.  Example AEI 1.5 CI 1.3 = SI 1.7.  The sire is better than the other sires presented to that group of mares.  Or AEI 1.5 CI 1.8 = SI 1.2  That sire is still above average, but the class of mares he receives inflates his AEI.  This works in most cases and shows where farms have used their high class mares to build up their young stallions.  One big anomaly in looking at stallions is Giants Causeway.  His AEI is around 2.00, but the mares CI is around 3.00 which computes to Giants Causeway being 1.00, a very average sire.  I think not!!!    

old old cat 08 May 2013 6:37 PM

Being a huge admirer of AP Indy , I was thrilled to see his grandson, Orb win the Derby ! Orb had the perfect Derby pedigree . It was also deeply moving to see Orb in the colors of Ruffian ,from whom he shares a direct female line family with !

Weekend Surprise 09 May 2013 12:08 AM

In response to Old Old Cat, I appreciate your analysis. Your mention of Giants Causeway raises the question, I wonder if there is actually a correlation of the CI to the sires AEI.  i.e. the general principle is "breed the best to the best..." but do the numbers add up, in general, all things considered?  In the case of a Giants Causeway, does that great pool of mares actually produce superior runners?  Does any sire maintain a knockout AEI when bred to mares with a CI over 3.0 or is regression to the mean inevitable?  Finally, of that pool of mares that GC was bred to was it the great running mares that produced the standout runners?  If so, it would be very helpful analysis because it would say to the lower class mare that breeding to such a sire might actually produce something special.


Joltman 09 May 2013 1:14 PM

Relating to the above, the nicking analysis might be of special interest in that perhaps there were mares who were great runners but outperformed by broodmares who were lesser runners, but better nick ratings.  


Joltman 09 May 2013 10:03 PM

In the past I did something similar to Old Old cat. I created a coefficient that was the result of dividing AEI^2 by CI. If you analyse it like this, you will notice that there is a bigger stress in quality than simply dividing AEI/CI.

however, the best comparison I've found after many years of study is to compare the average timeform of the progeny of a sire, against the average timeform of the production of the mares covered by that stallion with other sires. The problem with dollars or Euros is that a Dubai world cup winner will change strongly the AEI of a stallion. Regarding time form or Better Speed figures, the difference between a brilliant g1 winner and a claimer is not so big in terms of number. If a mare has 7 products and one g1 winner bsf 120 and the others worth 80, the average for the mare is 85 which is quite true.


Alfonso of spain 01 Jul 2013 12:45 PM

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