Adolphe Quetelet

Lambert Adolphe Jacques Quételet (February 22, 1796 – February 17, 1874) was a Flemish astronomer, mathematician, statistician and sociologist. He founded and directed the Brussels Observatory and was influential in introducing statistical methods to the social sciences. Some French-language sources give his last name as Quetelet, with no accent.

Biography and Education
Lambert Adolphe Jacques Quetelet was born in Gent, Belgium, on 22 February 1796. He studied at the lycée in Gent, where he started teaching mathematics in 1815, at the age of 19. In 1819 he moved to the athenaeum in Brussels and in the same year he completed his dissertation (De quibusdam locis geometricis, necnon de curva focal - Of some new properties of the focal distance and some other curves). He became a member of the Royal Academy in 1820. He lectured at the museum for sciences and letters and at the Belgian Military School. His scientific research encompassed a wide range of different scientific disciplines: meteorology, astronomy, mathematics, statistics, demography, sociology, criminology and history of science. He made significant contributions to scientific development, but he also wrote several monographs directed to the general public. He founded the Belgian Observatory, founded or co-founded several national and international statistical societies and scientific journals, and presided over the first series of the International Statistical Congresses. Quetelet was a liberal and an anticlerical, but not an atheist or materialist nor a socialist. In 1855 Quetelet suffered from apoplexy, which diminished but did not end his scientific activity. He died in Brussels on 17 February 1874.

Quetelet received a doctorate in mathematics in 1819 from the University of Ghent. Shortly thereafter, the young man set out to convince government officials and private donors to build an astronomical observatory in Brussels; he succeeded in 1828.

Sociology
The new science of probability and statistics was mainly used in astronomy at the time, to get a handle on measurement errors with the method of least squares. Quetelet was among the first who attempted to apply it to social science, planning what he called a "social physics". He was keenly aware of the overwhelming complexity of social phenomena, and the many variables that needed measurement. His goal was to understand the statistical laws underlying such phenomena as crime rates, marriage rates or suicide rates. He wanted to explain the values of these variables by other social factors. These ideas were rather controversial among other scientists at the time who held that it contradicted a concept of freedom of choice.

His most influential book was Sur l'homme et le développement de ses facultés, ou Essai de physique sociale, published in 1835 (In English translation, entitled Treatise on Man). In it, he outlines the project of a social physics and describes his concept of the "average man" (l'homme moyen) who is characterized by the mean values of measured variables that follow a normal distribution. He collected data about many such variables.

Criminology
Quetelet was an influential figure in criminology. Along with Andre-Michel Guerry, he helped to establish the cartographic school and positivist schools of criminology which made extensive use of statistical techniques. Through statistical analysis, Quetelet gained insight into the relationships between crime and other social factors. Among his findings were strong relationships between age and crime, as well as gender and crime. Other influential factors he found included climate, poverty, education, and alcohol consumption, with his research findings published in Of the Development of the Propensity to Crime.

Public health
Principal among these, in terms of influence over later public health agendas, was Quetelet's establishment of a simple measure for classifying people's weight relative to an ideal weight for their height. His proposal, the body mass index (or Quetelet index), has endured with minor variations to the present day. It remains the only widely-recognised raw material for obesity statistics and the policy discussions related to them.

Quetelet also founded several statistical journals and societies, and was especially interested in creating international cooperation among statisticians.

Other references

 * Stigler: "Statistics on the Table", Harvard University Press 1999, chapter 2
 * Ball, Philip: "Critical Mass: How One Thing Leads to Another", Arrow Books 2005, chapter 3