Demography (from prefix demo- from Ancient Greek δῆμος dēmos meaning "the people", and -graphy from γράφω graphō, implies "writing, description or measurement") is the statistical study of populations, especially human beings. As a very general science, it can analyze any kind of dynamic living population, i.e., one that changes over time or space (see population dynamics). Demography encompasses the study of the size, structure, and distribution of these populations, and spatial or temporal changes in them in response to birth, migration, aging, and death. Based on the demographic research of the earth, earth's population up to the year 2050 and 2100 can be estimated by demographers. Demographics are quantifiable characteristics of a given population.
Sociology is the scientific study of society, including patterns of social relationships, social interaction, and culture. It is a social science that uses various methods of empirical investigation and critical analysis to develop a body of knowledge about social order, acceptance, and change or social evolution. Many sociologists aim to conduct research that may be applied directly to social policy and welfare, while others focus primarily on refining the theoretical understanding of social processes. Subject matter ranges from the micro-sociology level of individual agency and interaction to the macro level of systems and the social structure.
Anyone who has studied psychology, sociology, anthropology, or any of the other wacko-and-wog disciplines knows the three great rules of the social sciences: Folks do lots of things. We don't know why. Test on Friday.
P.J. O'Rourke (2007) Age and Guile Beat Youth, Innocence, and a Bad Haircut. p. 207
Comte gave a powerful impetus to the development of sociology, an impetus which bore fruit in the later decades of the nineteenth century. To say this is certainly not to claim that French sociologists such as Durkheim were devoted disciples of the high priest of positivism. But by insisting on the irreducibility of each of his basic sciences to the particular science of sciences which it presupposed in the hierarchy and by emphasizing the nature of sociology as the scientific study of social phenomena Comte put sociology on the map. To be sure, [its] beginnings can be traced back well beyond Montesquieu, for example, and to Condorcet, not to speak of Saint-Simon, Comte's immediate predecessor. But Comte's clear recognition of sociology as a particular science, with a character of its own, justified Durkheim in regarding him as the father or founder of this science, in spite of the fact that Durkheim did not accept the idea of the three states and criticized Comte's approach to sociology.
Frederick Copleston A History of Philosophy: IX Modern Philosophy (1994). Image Books, New York. p. 140. ISBN 0385129106.