Demography

Statistic and scientific study of population is called Demography. It is a new science in study among other science. Achillle Guillard was the first person who used the term Demography in 1855 in his book Elements de Statistique Humaine on Demography Comparee. The term Demography is derived from two Greek words, Demos, means people and Graphein, to draw or write. Guillard used the term to denote mathematical knowledge of the social, intellectual, physical and ethical aspects of a population.  Demography stands for measurements by statistical methods of various characteristics of human population. Its principle concern is with population size, distribution and growth of population of a region, nation and the world. The constituents of growth of change are births, deaths and migration. Therefore, a demographer's primary concern is with fertility, mortality and population transfer from one region to another. They take keen interest in studying interaction between social, economic and political activities and demography related processes as size, distribution, composition and change in number determined by fertility, mortality and migration.

The demographer study populations with all their characteristics both at a single point and at different points of time. Whereas the former provides valuable information for comparing various population groups spread over space age and sex composition, vital rates, generic composition the latter provides an opportunity to study relation between two population in an area at two points of time, that is those aged x at a time t are survivors of those aged x-n at the time t-n, subject to mortality and migration. This helps projection of population and its composition, changes in birth and death rates and also changes in expectation of life at different ages.

John Graunt was known as founding father of modern demography. Graunt's book Natural and Political Observation Made upon the Bills of Mortality was the first-ever book on experimental and theoretical demography. From the records preserved in churches and cemeteries in London and around, Graunt studied in great details the information recorded for each married and deceased person and analyzed the collected information and tried to estimate, birth, death, marriage, migration rates and their interdependence. Graunt noted that the sex ratio at birth favored male babies. He also noted mortality changes with age. He also observed variations in mortality and causes of mortality with time and space. Based even on utterly inadequate information, Graunt prepared a table for age-specific death rate. This can be regarded as the true ancestor of modern Life table.

William Petty went a step further and tried to relate various population statistics to social, political and economic backdrop. Even with improved techniques of analyze and interpret many population issues. Petty tried to find answer to some such complex issues even though there was no apt technology to support his analysis and research. He tried population projections, and to show how urbanization was related to economic and social structure, to understand population structure and distribution in relation to active age group in the population, he gave considerable thought to problems of unemployment and partial employment and other social problems and tried to estimate gross national productivity.