Toru Hanai/Reuters
Elderly and middle-aged people exercise with wooden dumbbells during a health promotion event to mark Japan's "Respect for the Aged Day" at a temple in Tokyo's Sugamo district, an area popular among the Japanese elderly, Japan, September 18, 2017.
All around the world, countries are seeing dwindling birth rates and rising life expectancy. Aging populations are leading to greater spending on healthcare and pensions, but the number of people working and paying taxes is steadily going down. As a result, these countries are at risk of becoming "demographic time bombs," signifying a crisis of too few working people.
Demographers say countries need fertility rates of 2.2 children per woman to maintain a stable population, but many nations' birth rates, such as those of South Korea and the United States, have fallen below 2.
An increase in immigrant workers can help alleviate these trends, but immigration alone can't reverse a demographic time bomb if a significant number of citizens leave for employment in other countries.
Some places, such as the town of La Estrella in Spain, already reveal what a demographic time bomb can look like - a decreasing population, a large number of elderly people, and few children.
Here are some of the countries most at risk of becoming demographic time bombs: