Dosage Index
Encyclopedia
The Dosage Index is a mathematical figure used by breeders of Thoroughbred
race horses, and sometimes by bettors handicapping horse races, to quantify a horse's ability, or inability, to negotiate the various distances at which horse races are run. It is calculated based on an analysis of the horse's pedigree.
Interest in determining which sires of race horses transmit raw speed, and which sires transmit stamina (defined as the ability to successfully compete at longer distances) to their progeny dates back to the early 20th Century, when a French
researcher, Lt. Col. J. J. Vullier, published a study on the subject (called Dosage), which was subsequently modified by an Italian
breeding expert, Dr. Franco Varola, in two books he authored, entitled Typology Of The Race Horse and The Functional Development Of The Thoroughbred.
However, these observations attracted little interest from the general public until 1981, when Daily Racing Form
breeding columnist Leon Rasmussen published a new version of Dosage developed by an American scientist and horse owner, Steven A. Roman, Ph.D., in his analysis of the upcoming Kentucky Derby
for that year. The new approach, which was more accessible to owners, breeders and handicappers and was supported by solid statistical data, rapidly caught on, and the term "Dosage Index" has been a fixture in the lexicon of horse racing
ever since. The details of Dosage methodology have been summarized in Dr. Roman's book entitled Dosage: Pedigree & Performance published in 2002.
The index itself is compiled by noting the presence of certain influential sires, known as chefs-de-race (French
for "chiefs of racing," or, more esoterically, "masters of the breed") in the first four generations of a horse's pedigree. Based on what distances the progeny of the sires so designated excelled in during their racing careers (the distance preferences displayed by the sires themselves while racing being irrelevant), each chef-de-race (the list released in the early 1980s identified 120 such sires, and 85 more have been added ) is placed in one or two of the following categories, or "aptitudinal groups": Brilliant, Intermediate, Classic, Solid or Professional, with "Brilliant" indicating that the sire's progeny fared best at very short distances and "Professional" denoting a propensity for very long races on the part of the sire's offspring, the other three categories ranking along the same continuum in the aforementioned order. If a chef-de-race is placed in two different aptitudinal groups, in no case can the two groups be more than two positions apart; for example, Classic-Solid or Brilliant-Classic are permissible, but Brilliant-Solid, Intermediate-Professional and Brilliant-Professional are not.
If a horse's sire is on the chef-de-race list, it counts 16 points for the group to which the sire belongs (or eight in each of two categories if the sire was placed in two groups); a grandsire counts eight points, a great-grandsire four, and a great-great-grandsire two (female progenitors do not count directly, but if any of their sires etc. are on the chef-de-race list points would accrue via such sires).
This results in a Dosage Profile consisting of five separate figures, listed in order of Brilliant-Intermediate-Classic-Solid-Professional. Secretariat, the 1973 Triple Crown
winner, for example, had a Dosage Profile of 20-14-7-9-0. To arrive at the Dosage Index, the first two figures plus one-half the value of the third figure are added together, and then divided by one-half of the third figure plus the sum of the last two figures. In this case, it would be 37.5 (20 + 14+ 3.5) divided by 12.5 (3.5 + 9 + 0), giving Secretariat a Dosage Index of exactly 3.00 (the figure almost always being expressed with two places to the right of the decimal point and rounded to the nearest .01).
A second mathematical value, called the Center of Distribution, can also be computed from the Dosage Profile. To determine this value, the number of Brilliant points in the profile is doubled, and added to the number of Intermediate points; from this is then subtracted the number of Solid points and twice the number of Professional points. The result is then divided by the total number of points in the entire profile, including the Classic points. In Secretariat's case, this would work out as 54 (40 + 14) minus 9 (9 + 0) divided by 50 (20 + 14 + 7 + 9 + 0), yielding a Center of Distribution of 0.90 (the figure nearly always being rounded to the nearest 100th of a point, as with the Dosage Index).
High Dosage Index (and Center of Distribution) figures are associated with a tendency to perform best over shorter distances, while low numbers signify an inherent preference for longer races. The median Dosage Index of contemporary North American thoroughbred
s is estimated at 2.40 (the average figure being impossible to calculate because some horses have a Dosage Index of "infinity," a scenario which arises when a horse has only Brilliant and/or Intermediate chef-de-race influences in its Dosage Profile). The average Center of Distribution for modern-day North American race horses is believed to be approximately 0.70 (both Dosage Index and Center of Distribution figures tend to be lower for European thoroughbreds because in Europe the races are longer on aggregate and European breeders thus place greater emphasis on breeding their horses for stamina rather than speed).
Retroactive research conducted at the time the term "Dosage Index" first became common knowledge revealed that no horse having a Dosage Index of higher than 4.00 had won the Kentucky Derby
since at least 1929 (a year chosen because by then the number of available of chefs-de-race on which to base the figures was thought to have reached a critical mass), and that over the same period only one Belmont Stakes
winner (Damascus in 1967) had such a Dosage figure. It was also determined at that time that few horses with no chef-de-race influences in the two most stamina-laden groups, Solid and Professional, had won major races at distances of 1¼ miles or longer even if the horse had a sufficient Classic presence in its pedigree to keep the Dosage Index from being over 4.00 (when Affirmed
won the Triple Crown
in 1978, for instance, he became the first horse with no Solid or Professional points in his Dosage Profile to win either the Kentucky Derby
or the Belmont Stakes
since the 1930s). In recent years, however, several horses with no Solid or Professional chefs-de-race in the first four generations of their pedigrees — and indeed, a few with Dosage Indexes of above 4.00 — have managed to win the Kentucky Derby
and Belmont Stakes
, highlighting the issue of increasing speed and decreasing stamina in contemporary American thoroughbred pedigrees. For example, 2005 Kentucky Derby winner Giacomo
has a Dosage Index of 4.33 and no Solid or Professional points in his Dosage Profile. As a result of these "anomalies," the theory's usefulness has been questioned by some, at least with regard to the Kentucky Derby. The system's defenders, however, point out that in recent times a large proportion of U.S.-bred horses with low Dosage figures have been sent to race in foreign countries where the distances of races are longer, resulting in most horses competing in the Kentucky Derby and similar American races having relatively high Dosage numbers and/or lacking Solid or Professional chef-de-race representation. Yet the statistical foundation of Dosage remains compelling and the theory accurately differentiates Thoroughbred pedigree type for large populations of horses competitively performing over a range of distances, track surfaces and ages.
To find the Dosage Index of a horse:
Thoroughbred
The Thoroughbred is a horse breed best known for its use in horse racing. Although the word thoroughbred is sometimes used to refer to any breed of purebred horse, it technically refers only to the Thoroughbred breed...
race horses, and sometimes by bettors handicapping horse races, to quantify a horse's ability, or inability, to negotiate the various distances at which horse races are run. It is calculated based on an analysis of the horse's pedigree.
Interest in determining which sires of race horses transmit raw speed, and which sires transmit stamina (defined as the ability to successfully compete at longer distances) to their progeny dates back to the early 20th Century, when a French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
researcher, Lt. Col. J. J. Vullier, published a study on the subject (called Dosage), which was subsequently modified by an Italian
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
breeding expert, Dr. Franco Varola, in two books he authored, entitled Typology Of The Race Horse and The Functional Development Of The Thoroughbred.
However, these observations attracted little interest from the general public until 1981, when Daily Racing Form
Daily Racing Form
The Daily Racing Form is a tabloid newspaper founded in 1894 in Chicago, Illinois by Frank Brunell. The paper publishes the past performances of race horses as a statistical service for bettors on horse racing in the United States....
breeding columnist Leon Rasmussen published a new version of Dosage developed by an American scientist and horse owner, Steven A. Roman, Ph.D., in his analysis of the upcoming Kentucky Derby
Kentucky Derby
The Kentucky Derby is a Grade I stakes race for three-year-old Thoroughbred horses, held annually in Louisville, Kentucky, United States on the first Saturday in May, capping the two-week-long Kentucky Derby Festival. The race is one and a quarter mile at Churchill Downs. Colts and geldings carry...
for that year. The new approach, which was more accessible to owners, breeders and handicappers and was supported by solid statistical data, rapidly caught on, and the term "Dosage Index" has been a fixture in the lexicon of horse racing
Horse racing
Horse racing is an equestrian sport that has a long history. Archaeological records indicate that horse racing occurred in ancient Babylon, Syria, and Egypt. Both chariot and mounted horse racing were events in the ancient Greek Olympics by 648 BC...
ever since. The details of Dosage methodology have been summarized in Dr. Roman's book entitled Dosage: Pedigree & Performance published in 2002.
The index itself is compiled by noting the presence of certain influential sires, known as chefs-de-race (French
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...
for "chiefs of racing," or, more esoterically, "masters of the breed") in the first four generations of a horse's pedigree. Based on what distances the progeny of the sires so designated excelled in during their racing careers (the distance preferences displayed by the sires themselves while racing being irrelevant), each chef-de-race (the list released in the early 1980s identified 120 such sires, and 85 more have been added ) is placed in one or two of the following categories, or "aptitudinal groups": Brilliant, Intermediate, Classic, Solid or Professional, with "Brilliant" indicating that the sire's progeny fared best at very short distances and "Professional" denoting a propensity for very long races on the part of the sire's offspring, the other three categories ranking along the same continuum in the aforementioned order. If a chef-de-race is placed in two different aptitudinal groups, in no case can the two groups be more than two positions apart; for example, Classic-Solid or Brilliant-Classic are permissible, but Brilliant-Solid, Intermediate-Professional and Brilliant-Professional are not.
If a horse's sire is on the chef-de-race list, it counts 16 points for the group to which the sire belongs (or eight in each of two categories if the sire was placed in two groups); a grandsire counts eight points, a great-grandsire four, and a great-great-grandsire two (female progenitors do not count directly, but if any of their sires etc. are on the chef-de-race list points would accrue via such sires).
This results in a Dosage Profile consisting of five separate figures, listed in order of Brilliant-Intermediate-Classic-Solid-Professional. Secretariat, the 1973 Triple Crown
Triple Crown of Thoroughbred Racing
The Triple Crown of Thoroughbred Racing consists of three races for three-year-old Thoroughbred horses. Winning all three of these Thoroughbred horse races is considered the greatest accomplishment of a Thoroughbred racehorse...
winner, for example, had a Dosage Profile of 20-14-7-9-0. To arrive at the Dosage Index, the first two figures plus one-half the value of the third figure are added together, and then divided by one-half of the third figure plus the sum of the last two figures. In this case, it would be 37.5 (20 + 14+ 3.5) divided by 12.5 (3.5 + 9 + 0), giving Secretariat a Dosage Index of exactly 3.00 (the figure almost always being expressed with two places to the right of the decimal point and rounded to the nearest .01).
A second mathematical value, called the Center of Distribution, can also be computed from the Dosage Profile. To determine this value, the number of Brilliant points in the profile is doubled, and added to the number of Intermediate points; from this is then subtracted the number of Solid points and twice the number of Professional points. The result is then divided by the total number of points in the entire profile, including the Classic points. In Secretariat's case, this would work out as 54 (40 + 14) minus 9 (9 + 0) divided by 50 (20 + 14 + 7 + 9 + 0), yielding a Center of Distribution of 0.90 (the figure nearly always being rounded to the nearest 100th of a point, as with the Dosage Index).
High Dosage Index (and Center of Distribution) figures are associated with a tendency to perform best over shorter distances, while low numbers signify an inherent preference for longer races. The median Dosage Index of contemporary North American thoroughbred
Thoroughbred
The Thoroughbred is a horse breed best known for its use in horse racing. Although the word thoroughbred is sometimes used to refer to any breed of purebred horse, it technically refers only to the Thoroughbred breed...
s is estimated at 2.40 (the average figure being impossible to calculate because some horses have a Dosage Index of "infinity," a scenario which arises when a horse has only Brilliant and/or Intermediate chef-de-race influences in its Dosage Profile). The average Center of Distribution for modern-day North American race horses is believed to be approximately 0.70 (both Dosage Index and Center of Distribution figures tend to be lower for European thoroughbreds because in Europe the races are longer on aggregate and European breeders thus place greater emphasis on breeding their horses for stamina rather than speed).
Retroactive research conducted at the time the term "Dosage Index" first became common knowledge revealed that no horse having a Dosage Index of higher than 4.00 had won the Kentucky Derby
Kentucky Derby
The Kentucky Derby is a Grade I stakes race for three-year-old Thoroughbred horses, held annually in Louisville, Kentucky, United States on the first Saturday in May, capping the two-week-long Kentucky Derby Festival. The race is one and a quarter mile at Churchill Downs. Colts and geldings carry...
since at least 1929 (a year chosen because by then the number of available of chefs-de-race on which to base the figures was thought to have reached a critical mass), and that over the same period only one Belmont Stakes
Belmont Stakes
The Belmont Stakes is an American Grade I stakes Thoroughbred horse race held every June at Belmont Park in Elmont, New York. It is a 1.5-mile horse race, open to three year old Thoroughbreds. Colts and geldings carry a weight of 126 pounds ; fillies carry 121 pounds...
winner (Damascus in 1967) had such a Dosage figure. It was also determined at that time that few horses with no chef-de-race influences in the two most stamina-laden groups, Solid and Professional, had won major races at distances of 1¼ miles or longer even if the horse had a sufficient Classic presence in its pedigree to keep the Dosage Index from being over 4.00 (when Affirmed
Affirmed
Affirmed was an American Thoroughbred racehorse who was the eleventh and most recent winner of the United States Triple Crown of Thoroughbred Racing...
won the Triple Crown
Triple Crown of Thoroughbred Racing
The Triple Crown of Thoroughbred Racing consists of three races for three-year-old Thoroughbred horses. Winning all three of these Thoroughbred horse races is considered the greatest accomplishment of a Thoroughbred racehorse...
in 1978, for instance, he became the first horse with no Solid or Professional points in his Dosage Profile to win either the Kentucky Derby
Kentucky Derby
The Kentucky Derby is a Grade I stakes race for three-year-old Thoroughbred horses, held annually in Louisville, Kentucky, United States on the first Saturday in May, capping the two-week-long Kentucky Derby Festival. The race is one and a quarter mile at Churchill Downs. Colts and geldings carry...
or the Belmont Stakes
Belmont Stakes
The Belmont Stakes is an American Grade I stakes Thoroughbred horse race held every June at Belmont Park in Elmont, New York. It is a 1.5-mile horse race, open to three year old Thoroughbreds. Colts and geldings carry a weight of 126 pounds ; fillies carry 121 pounds...
since the 1930s). In recent years, however, several horses with no Solid or Professional chefs-de-race in the first four generations of their pedigrees — and indeed, a few with Dosage Indexes of above 4.00 — have managed to win the Kentucky Derby
Kentucky Derby
The Kentucky Derby is a Grade I stakes race for three-year-old Thoroughbred horses, held annually in Louisville, Kentucky, United States on the first Saturday in May, capping the two-week-long Kentucky Derby Festival. The race is one and a quarter mile at Churchill Downs. Colts and geldings carry...
and Belmont Stakes
Belmont Stakes
The Belmont Stakes is an American Grade I stakes Thoroughbred horse race held every June at Belmont Park in Elmont, New York. It is a 1.5-mile horse race, open to three year old Thoroughbreds. Colts and geldings carry a weight of 126 pounds ; fillies carry 121 pounds...
, highlighting the issue of increasing speed and decreasing stamina in contemporary American thoroughbred pedigrees. For example, 2005 Kentucky Derby winner Giacomo
Giacomo
Giacomo is a Thoroughbred stallion race horse trained by John Shirreffs who is perhaps best known for winning the 2005 Kentucky Derby in 2:02.75...
has a Dosage Index of 4.33 and no Solid or Professional points in his Dosage Profile. As a result of these "anomalies," the theory's usefulness has been questioned by some, at least with regard to the Kentucky Derby. The system's defenders, however, point out that in recent times a large proportion of U.S.-bred horses with low Dosage figures have been sent to race in foreign countries where the distances of races are longer, resulting in most horses competing in the Kentucky Derby and similar American races having relatively high Dosage numbers and/or lacking Solid or Professional chef-de-race representation. Yet the statistical foundation of Dosage remains compelling and the theory accurately differentiates Thoroughbred pedigree type for large populations of horses competitively performing over a range of distances, track surfaces and ages.
External links
For a more detailed explanation of the Dosage Index:To find the Dosage Index of a horse: