Cambridge University Press, 1987.
Prediction is very difficult, especially about the future.
Demographics is the study of population. Malthus was one of the first to predict critical consequences for society as a result of overpopulation. In most of the developed countries in the 1980s, ZPG has been achieved. The United States has reached this goal. For example, there are so many members of the baby boom generation, that their retirement will create chaos in our society.