Sorokin reviewed the literature on population and recognised the importance of sociological studies of population. Box 1.2 presents Sorokin's conclusion of the survey of literature of demographic school. To Sorokin size, density, heterogeneity and mobility are factors that affect ideas, institutions and history in complex ways.

KINGSLEY DAVIS

Kingsley Davis linked the population growth with development and migration. Kingsley Davis is famous for his theory of change and response (also called theory of multiphasic response) according to which economic and technological developments and subsequent fall in mortality led to various responses among people which resulted in low fertility. These responses include increasing use of birth control methods, increased celibacy, postponement of marriage, practice of abortion and emigration. Improvement in mortality in Japan and pre-transitional Europe increased family size and as time passed people could perceive the stress of increasing family size on family resources (Davis , 1963). In this context, people started exploring various ways of limiting family size. Davis is a functionalist and he shows how disturbance created by a factor of social change (e.g. mortality) leads to changes in individual behaviour (limiting family size) which eventually restores the equilibrium (zero population growth).