Demographic window

This occurs when the demographic architecture of a population becomes younger and the percentage of people able to work reaches its height.

Because of the mechanical link between fertility levels and age structures, the timing and duration of this period is closely associated to those of fertility decline: when birth rates fall, the age pyramid first shrinks with gradually lower proportions of young population (under 15s) and the dependency ratio decreases as is happening (or happened) in various parts of East Asia over several decades.

After a few decades, low fertility however causes the population to get older and the growing proportion of elderly people inflates again the dependency ratio as is observed in present-day Europe.

The Global Data Lab released an alternative classification of phases:[1] Europe's demographic window lasted from 1950 to 2000.

India is expected to enter the demographic window in 2010, which may last until the middle of the present century.

Inverse dependency ratios in world regions, showing US window 1970–2030 and East Asian window 1980–2040
Demographic Phase as per the classification of the Global Data Lab for 1,921 area's in Less Developed Countries