The Truth of the Matter

Last June I posted some statistics on the question of whether dams were more important than sires. The statistics did NOT corroborate this supposition.

One of the reasons for that result was a flaw in the definition of “elite” sires, which for purposes of that study consisted of all G1 stakes winners (with all other sires being considered “nonelite”). At the time I suggested that a different definition of “elite” sires (not related to racing class) might produce a different result.

So I returned to this idea with a different definition of “elite” sires. This time I am using market prices to define which sires are “better” than others. Here is how it works.

I defined A (“better”) sires as those who had at least ten sales foals (weanlings, yearlings, and two-year-olds) in a given year, and those foals averaged $50,000-$99,999. I defined B (“good”) sires as those who had at least ten sales foals (ditto) in a given year, and those foals averaged $10,000-$49,999.

To even the playing field, I considered only those foals by both sets of sires that sold between $20,000 and $50,000 inclusive. So the foals by A sires in this group were at the lower end of their sires’ sales prices. And the foals by B sires in this group were at the higher end of their sires’ sales prices.

So the foals in this group by A sires were by better sires out of good dams. Call that group AB. The foals in this group by B sires were by good sires out of better dams. Call that group BA.

One of the points of this exercise was to determine which is the better buying strategy, to purchase cheaper foals by better sires or to purchase more expensive foals by cheaper sires. The AB group (sires better than dams) corresponds to sires being more important than dams. The BA group (dams better than sires) corresponds to dams being more important than sires.

Perhaps a concrete example will illuminate this idea. Mine That Bird (Birdstone–Mining My Own, Smart Strike) won the 2009 Kentucky Derby at odds of 50-1. Earlier that year (on February 8) the unraced Mining My Own had produced a colt by Even the Score. When that colt came up for sale at the 2010 Keeneland September yearling sale, he brought a pretty good price ($250,000) because he was a half-brother to the previous year’s Kentucky Derby winner. Even the Score had ten yearlings sold in 2010. The next highest price was only $39,000. The overall average for those ten yearlings was only $33,710, and the median was $4,350.

That of course is the way the breeding industry works. At the time the decision was made to breed Mining My Own to Even the Score in 2008, Mine That Bird had not even raced yet. In the two years between the decision to breed that mare to that sire the value of the mare (and of the resultant foal) increased significantly, thanks to Mine That Bird. The resultant foal by Even the Score was named Dullahan and became a G1 winner.

Dullahan is a rather extreme example of a “better” mare being bred to a lower-ranking sire. The fact that Dullahan became a G1 winner is evidence in favor of the supposition that the dam is more important than the sire. The BA group represents higher-value mares being bred to lower-value sires. The AB group represents lower-value mares being bred to higher-value sires. If the BA group has better results than the AB group relative to their respective prices, the supposition that dams are more important than sires is reinforced.

Having explained all that, let us now examine the prices for the two groups.

Group          Foals          Average          Maverage          Price Index

AB                2,238          $33,924            182.13                    1.18

BA                3,460          $30,581             171.71                     1.11

By design the two groups are pretty close in prices. That is because both groups consist only of foals that sold between $20,000 and $50,000 inclusive. AB is slightly higher than BA by all three measures, which is to be expected.

Now let us examine the racetrack results for the two groups. APPPSW stands for average Performance Points per stakes winner, a measure of the quality of stakes winners involved, with the average now being 687.

Group          Foals          Stakes Winners          %          APPPSW          PPI (Result)

AB                2,238                    93                      4.16            650                     1.17

BA                3,460                   138                     3.99            665                     1.15

AB was slightly better than BA (4.16% to 3.99%) by percentage of stakes winners from foals. BA was slightly better than AB (665 to 650) by APPPSW. Taking both quantity and quality of stakes winners into account, AB was slightly better than BA (1.17 to 1.15) by PPI.

So BA was NOT better than AB. You could infer from this that dams are NOT more important that sires.

If you take prices into account, however, BA WAS slightly better than AB. AB had a price of 1.18 and a result of 1.17 (very slightly negative). BA had a price of 1.11 and a result of 1.15 (very slightly positive). If you look at it from that point of view, you could claim that dams are more important than sires. BA had BETTER results than prices. AB was the opposite.

The truth of the matter is that both groups had results that were very close to their prices. It is almost too close to call. It is too close to call it a definitive victory for the supposition that dams are more important than sires. It might be a very minor victory for that supposition, but that is about all.

The safest thing to say is that the assumption that sires and dams are 50-50 is not seriously challenged here. Maybe one is slightly more important than the other, but not by much (say 51-49). If you want to accept the supposition that one is radically more important than the other, you are certainly entitled to your opinion. But that is merely an opinion. It is not a proven fact.

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