science that deals with populations and their structures statistically and theoretically
Demography studies the statistics of human populations. Demography is usually used to study dynamic (constantly changing) populations. It covers the study of the size, structure and distribution of these populations and the changes in these populations due to births, deaths, migration and emigration. Demography can also be applied to entire groups defined by nationality, religion and ethnicity.
Formal demography limits its object of study to the measurement of populations processes, while the more broad field of social demography population studies also analyze the relationships between economic, social, cultural and biological processes influencing a population.