Population projections: goals, methods, hypotheses.

Population projections generally use the component method which consists in adapting sample size by age and sex from mortality, fertility, and migration hypotheses. This exercise is nor always aimed a providing projection data, but may also serve to analyze factors changing in the population. Comparatively long-term demographic forecasts, particularly for mortality, can be made due to the major inertia of demographic phenomena. However, the quality of such predictions depends on the quality of knowledge of past evolution in the demographic factors and on the capacity to forecast their future evolution.