Best Answer:
In the middle of the twentieth century, demographic transition theory became the dominant theory of population growth. Based on observed trends in Western European societies, it argues that populations go through three stages in their transition to a modern pattern. Stage One (pretransition) is characterized by low or no growth, and high fertility is counterbalanced by high mortality. In Stage Two (the stage of transition), mortality rates begin to decline, and the population grows at a rapid pace. By the end of this stage, fertility has begun to decline as well. However, because mortality decline had a head start, the death rate remains lower than the birth rate, and the population continues to experience a high rate of growth. In Stage Three (posttransition), the movement to low fertility and mortality rates is complete, producing once again a no-growth situation. The theory of demographic transition explains these three stages in terms of economic development, namely industrialization and urbanization. Since about 1980, demographic transition theory has been criticized on a number of grounds, including its assumption that the demographic experience of non-Western societies will inevitably follow that of the West; its failure to consider cultural variables; and its hypothesized relationship between population growth and economic development. Indeed, all three theories above contain assumptions about population growth and economic development; however, there is mounting evidence that this relationship is complex and varies from context to context. As the twenty-first century begins, the attempt to erect a general theory of population growth has been abandoned, signaling for some an alarming trend in population studies
