The Skinny on Overweights
When I used
to go to the races as a kid, I followed the same pattern. I’d get a program to
supplement my tattered and marked-up edition of the Daily Racing Form, find a comfortable table and chair in the gazebo
and accept the offer of an ice-cold Pepsi from my stepdad, Dennis.
Then,
sipping on our overpriced and oversweetened beverages, swapping various
sections of the Form like we were
assembling a great puzzle (which, in a sense, we were), both Dennis and I would
await track announcer Gary Henson to make his presence known.
“Welcome to
Longacres,” Henson would drawl in that distinctive, dulcet voice of his. “Here
are today’s overweights and changes.”
Like a
dutiful servant, I would note the information in my program. Mostly I cared
about the scratches, but I always wrote down the overweights as well.
“In the
sixth race, number two, Scamparina, is three pounds over… no changes in the
seventh race… in the eighth race, number five, My Satire, has been withdrawn…”
And so it
would go until my program was filled with all the latest updates.
At that
point, smiling smugly at my efficiency and attention to detail, I would proceed
to ignore all but the scratches and go about my day — not once, in 30+ years of
playing the races, have I ever altered my selections or list of contenders
based on a late change in weights.
Recently, I’ve
begun to wonder whether my dismissive attitude regarding this factor was/is
wise, so I decided to find out.
Using my
new, handy-dandy results chart database program, I examined 889 races — I didn’t
have the stamina for 890 — from various tracks across the country. My query was
simple: Do horses that are carrying more than their assigned weight, i.e.
overweights, win as often as they should?
Now, before
we go any further, let me explain the phrase “as often as they should.” Simply put, this means that horses showing a
specific characteristic — in this case, a greater race weight than assigned
weight — win their rightful share of races.
In his
masterful work “Winning At The Races,” Dr. William Quirin introduced the
concept of an “impact value,” which he calculated by “dividing the percentage
of winners with a given characteristic by the percentage of starters with that
characteristic.”
“An IV of
1.00 means that horses with a specific characteristic have won no more and no
less than their fair share of races,” Dr. Quirin explained.
Similarly, an IV of greater than 1.00 denotes that a particular factor is producing more than its fair share of winners, while an IV under 1.00 means that it is producing less.
Similarly, an IV of greater than 1.00 denotes that a particular factor is producing more than its fair share of winners, while an IV under 1.00 means that it is producing less.
In addition
to Dr. Quirin’s original impact value, I will also offer an odds-based impact
value when I present my findings later in this piece. The OBIV is based, not on
field size, but on the average odds of the horses meeting the criteria of the study.
The advantage of such an approach is that it better isolates the factor being
tested by equalizing the winning chances of the horses that show it.
For example, if one
were to test what effect the letter “a” in a race favorite’s name had on its
performance, it is abundantly clear to those who understand statistics that the
impact value would be high… not because the horse’s name contained the letter “a,”
mind you, but because the horse was favored.In fact, when I tested just such a proposition (race favorites with the letter “a” in their name) using my database, 579 horses qualified and the impact value was a staggering 2.78. Yet, the OBIV was only 0.81, which is right in line with expectations for race favorites as a whole (see graphic below).
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| (Click on image to enlarge) |
So, with all of that out of the way, let’s get on to the fun stuff — the study itself. The first thing I’ll post is how ALL of the horses in my survey of 889 races performed, just so we have some baseline statistics:
Horses – 6,790
Winners –
889
Rate – 13.1%
IV – 1.00
OBIV – 0.81
And now — drum roll,
please — we’ll see what happens when a horse is asked to carry more than its
assigned weight:
Horses – 1,010
Winners – 109
Rate – 10.8%
IV – 0.85
OBIV – 0.73
The results
are stunning — at least to me — as they appear to confirm that additional,
unassigned weight is, in fact, detrimental to a horse’s performance. Not only is the IV
less than 1.00, but the OBIV is also below the 0.80 “fairness” threshold.
I guess I
should have paid more attention to Gary Henson.
Weekend Handicapping Reports
SATURDAY (8/4)
SATURDAY (8/4)
2012 West Virginia Derby (MNR)
2012 Prioress Stakes (SAR)
2012 Whitney Stakes (SAR)
Fair Meadows Tulsa Win Factor Report
The Meadowlands Win Factor Report
2012 Prioress Stakes (SAR)
2012 Whitney Stakes (SAR)
Fair Meadows Tulsa Win Factor Report
The Meadowlands Win Factor Report
8 comments:
Very interesting Derek. I am working on a post about Lasix and it's effect on bodyweight - the study I am using shows that horses on the drug drop 28lbs of fluid in the 4hr time frame from injection to post time, where non lasix users only drop 12lbs. You think its fair to assume that extra 16lbs of bodyweight in non Lasix users is a performance hindrance?
Yet the druggies continue to sell the point that lasix isnt performance enhancing, hogwash.
That's a great study and it raises a point of contention I've had for years -- the weight of horses not being known.
As someone that went to the greyhound tracks when I was younger (the sport is all but dead), I remember that every dog was weighed in before it ran. I think it's a valuable piece of information.
Can you explain WHY a horse is asked, unexpectedly, to carry more weight? Jock just heavy? Was the horse's assigned weight originally wrong? I never understood. Would love ro know.
Generally, it's one of two reasons:
1) The jockey simply didn't make the assigned weight for whatever reason. The human population, as a whole, is getting bigger and heavier so a lot of riders are right at the borderline of some of these weight assignments to begin with, which brings up reason #2...
2) The jockey wasn't expected to make the assigned weight. There is a belief among some trainers that "live" weight is more desirable than "dead" weight and they will happily be a pound or two overweight rather than have too carry to much dead weight, or lead.
There ARE times when the assigned weight or program weight is wrong too, but that is rare.
Would overweights be more likely with the TOP jockey on a given circuit or the set of jockeys just hoping to score a mount? The answer to that may severely impact your analysis.
In other words, if the overweights were predominantly the lesser jockeys, and thus lesser horses, their IV as a group would be different than the IV of all horses that ran (including those with the good jockeys)
Right?
Yeah, the lower-tier jockeys and poorer horses would have lower impact values, but that's why I also posted the OBIV, which accounts for the odds.
Still, it would be interesting to see if there is a difference between good and poor overweight jockeys. That sounds like a future study...
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