As the average life span expands, if threshold ages, including the “normal” retirement age, are not properly adjusted the need for intergenerational transfers increases. Threshold ages can be raised in such a way that the proportion of the life span spent in the various phases (e.g., in youth Y*, adulthood A*, and old age S*) remains the same. Here is an example of what this criterion produces as e(0) increases from 60 to 86, while Y* (20%), A* (60%), and S* (20%) are kept constant.
World population