Figure 1. World population by age and sex: 1950–2050. Distribution of the world population by age and sex from 1950 (top panel) to 2000 (middle panel) and 2050 (bottom panel). With global aging, the world population is being transformed from a population pyramid to a population dome. These changes occur not only in developed countries (grey) but also in developing countries (white). Adopted from United Nations and United States Census Bureau.[1]^,[2].