Historical demography

Historical demography is a quantitative study of history of human population, developed and popularized in 20th century by French historian Louis Henry. It is considered both a supporting science of history and a part of demography.

Unlike modern demography, historical demography relies on data from before the statistical tools like censuses were introduced. Therefore it involves the systematic analysis of documents from parish and civil registers, from which estimates of fertility (birth rates), mortality (death rates), and other factors such as migration or marriage rates are made, yielding data about larger issues such as population change (growth and decline). Historical demography studies range from wide-ranging hypotheses to detailed community studies ("one-place studies").

Methodology
Unlike modern demography, historical demography relies on data from before the statistical tools like censuses were introduced. For prehistoric populations, population estimates rely on archaeological studies. For the later periods with written records but with no census of population or registration of births and deaths, it relies heavily on document analysis, looking at inscriptions on gravestones, church records of christenings, marriages and burials (parish registers), voter or citizenship rolls, legal documents (such as records of wills and deceased estates or land tenure records), taxation lists, muster lists for militia service and similar documets. In Western civilization, particularly Europe, ecclesiastical records of baptisms, marriages, and funerals serve as proxies for civil registration from the sixteenth century onward, until modern and more reliable civil statistical censuses and other records are used from 19th century onward. For other parts of the words, reliable data begun to be available much later.

Applications
This branch of sciences was first introduced by French historian Louis Henry (1911-1991) in his study of French population in the 17th century, although similar approaches were proposed by some historians earlier (John Graunt carried such studies as early as in 17th century, and Commission for Historical Demography, was founded as early as in 1928). It was nonetheless Louis Henry who manged to merge and popularize existing tools in such an innovative way that he came to be recognized as the founder of this new branch of historical and demography studies.

Historians saw the new discipline as a logical development and merger of scientific and quantitative history. For demographers, it contributed fundamental theoretical concepts, particularly in the area of fertility; fuelling the ongoing debate over population policies for the developing countries.

Various estimates of the historical sizes of the world population by continent were summarized by Jean-Noël Biraben in 1979. Later estimates are available from the publications of the United Nations and international agencies such as the World Bank.

Scientists using this approach include Philippe Ariès, Michel Fleury, Irena Gieysztorowa, Pierre Goubert, John Hajnal, Louis Henry, Marek Górny, Peter Laslett, Hervé Le Bras, Cezary Kuklo and Edmund Piasecki. In France, Annales School is the center of that research, in England, Cambridge group. Works of historical demography are published all over the world, in Canada, Sweden, Germany, the Netherlands, Spain and Poland.

Publications in the area of historical demography include the French Annales de la Demographie Historique and Polish Przeszłość Demograficzna Polski.

Two distinct schools exist in the approach to historical demography:
 * the French school, represented among others by Ariès, Fleury, Goubert and Le Bra, concentrates on Church records. By linking the names on the registers of baptisms, marriages, and funerals, they were able to reconstitute the histories of cohorts of families over the years. This method is known as family reconstitution.
 * the English school, represented among others by Laslett and Hajnal, concentrates on secular records such as censuses and tax records

Historical population of the world
During the period from 500 to 900 C.E. world population grew slowly but the growth rate accelerated between 900 and 1300 C.E. when the population doubled. During the fourteenth century, there was a fall in population associated with the Black Death that spread from Asia to Europe. This was followed by a period of restrained growth until the eighteenth century when world population entered a period of accelerated growth again. As previously the acceleration was more marked in the European population, due to scientific revolution and resulting inventions lowering the childbirth mortality rate. European population reached a peak growth rate of 10 per thousand per year in the second half of the nineteenth century. During the twentieth century, the growth rate among the European populations fell down and was overtaken by a rapid acceleration in the growth rate in other continents, which reached 21 per thousand per year in the last fifty years of the millennium. Between 1900 and 2000 C.E. the population of the world increased by 277 percent; the European component increased by 124 percent, and the remainder by 349 percent.

Related fields
A subfield of historical demography with a very narrow geographical scope is called a "one-place study". It is a branch of family history with a focus on the entire population of a single European village or community, not just a single, geographically dispersed family line.