fastest aging country elderly citizens post–World War II baby boom birth rates total fertility rate replacement rate world's lowest median age highest in the world Wa World War I Japanese World War II
Japan has a population of almost 125 million, of which nearly 122 million are Japanese nationals (2022 estimates). A small population of foreign residents makes up the remainder. 
Japan is the world's fastest aging country and has the highest proportion of elderly citizens of any country, comprising one-third of its total population; this is the result of a post–World War II baby boom, which was followed by an increase in life expectancy and a decrease in birth rates. Japan has a total fertility rate of 1.4, which is below the replacement rate of 2.1, and is among the world's lowest; it has a median age of 48.4, the highest in the world. As of 2020, over 28.7 percent of the population is over 65, or more than one in four out of the Japanese population. As a growing number of younger Japanese are not marrying or remaining childless, Japan's population is expected to drop to around 88 million by 2065.
