Between 2012 and 2050, the share of the world’s population age 65 and over is projected to double from 8 percent in 2012 to 16.7 percent in 2050 (see figure). Although the United States is also projected to age over this period, it will remain one of the youngest developed countries, with 20.9 percent of its population 65 and over in 2050.

In contrast, Japan is projected to continue to be the oldest country of those with a population greater than 50,000, with 40.1 percent age 65 and over in 2050. Other developed countries, including Germany, Italy, Spain and Poland, are expected to have nearly one-third of their populations age 65 and over.

Compared to the largest countries in the world, the United States had the greatest proportion of the population 65 and over in 2012, 13.7 percent compared with 9.1 percent in China and 5.6 percent in India. However, by 2050, China is projected to have surpassed the U.S. with a larger proportion of its population 65 and older (26.8 percent versus 20.9 percent).

Although a larger proportion of the U.S. population is currently in the older ages, China and India have much larger populations overall, including 65 and over. In 2012, China had 122 million and India had 67 million people 65 and over, compared with 43 million in the United States.

Growth in the proportion of the population in the oldest ages is driven by trends in fertility, mortality and international migration within each country.

Declines in fertility rates throughout much of the world have led to slower growth at the youngest ages. Decreases in mortality rates result in longer life expectancies and increases in the number of people that survive to the older ages, resulting in growth of the older population.

In the United States, international migration, which bolsters the size of the population between the working ages (18 to 64), is an important component keeping the United States among younger developed countries.

For more information about the Census Bureau’s projections for the United States, please visit: www.census.gov/population/projections. For information about the Census Bureau’s  projections for other countries, please visit: www.census.gov/population/international/data/idb.