SOURCE: US CENSUS BUREAU
Map & Data: US Census Bureau (@uscensusbureau)
Website: An Aging World: 2020 Story Map
Beyond The Map: On Aging: The Annual Conference of the American Society on Aging
Population aging is defined as the disproportionate growth of the older population in a society compared to the overall population. When such disproportionate growth occurs, older age groups will comprise an increasing portion of the total population. Population aging results from two underlying demographic changes: sustained fertility declines and increases in life expectancy.
Societal population aging is often measured by changes in the percentage of older people, or changes in the median age of the population (exactly half of the population will be above and below that age). The map on the right illustrates the variation in the percent 65 and older in countries of the world.
The Demographic Transition
The process of population aging is illustrated by a generalized model called the Demographic Transition. The demographic transition consists of five stages. This stylized figure identifies key phases when changes in fertility and mortality take place and shows their impact on population growth.
In Stage 1, both birth rates and death rates are high. The natural increase (births minus deaths) is low and population growth is minimal. Stage 2 marks a period of rapid declines in mortality, especially infant and child mortality. During this stage, fertility remains high, and the total population shows an early expansion. In Stage 3, fertility also begins a rapid decline, accompanied by continued yet slower mortality decline, during which the total population continues to grow. Population growth enters another stationary phase in Stage 4, with low rates of fertility and mortality. When death rates exceed birth rates, as in Stage 5, population growth starts declining.
Demographic trends of global aging
As explained in the previous section, population aging results from a decline in birth and death rates. The map shows the percentage-point increase in the share of the population over 65 years old from 2020 to 2050. Most countries outside of sub-Saharan Africa (Africa except for Northern Africa) are projected to experience increases in their older population of 5 percentage points or more.
Some of the already old countries in 2020 will continue to see rapid growth of the population 65 and older, with projected increases of higher than 10 percentage points. Examples include Japan (percent 65 and older in 2020 vs. 2050: 29.2, 40.1), Portugal (20.9; 32.5), South Korea (15.9; 34.7), Romania (17.6; 31.3), Cuba (15.8; 28.5), and many other European countries. On the other hand, possible pauses or reversals in fertility declines are projected for some countries with extremely low fertility levels, which are expected to slow down their aging process compared to those listed above. Some examples of these countries include Germany (percent 65 and older in 2020 vs. 2050: 23.0, 30.1), Greece (22.4; 31.5); or Italy (22.1; 31.0).
As Asia and Latin America continue their rapid speed for aging, of particular interest are countries that are currently relatively young but are projected to age quickly in the next three decades. Some examples include Mongolia (percent 65 and older in 2020 vs. 2050; 4.8, 16.7), Iran (5.9; 19.3), Jamaica (9.2; 24.6), or Brazil (9.2; 21.1).
In addition to fertility and mortality, migration can contribute to population aging, given that migration is most common among young adults (and that some adults take their children with them when they move). Migration tends to increase aging in the societies from which migrants originate and decrease aging in the societies that receive them.