Twenty percent of the population, or 25.56 million people, were aged 65 or older as of Thursday, up 0.5 percentage point from a year earlier, government statistics showed Sunday.
The ratio of those 65 or older in the overall population stood at 4.9 percent in 1950 and rose gradually to 10.3 percent in 1985. During the two decades since then, it went up rapidly to reach the 20 percent line this year for the first time, according to the Internal Affairs and Communications Ministry.
There were 10.81 million men in this age bracket, accounting for 17.4 percent of all Japanese men, while the corresponding figures for women were 14.75 million and 22.5 percent, according to the ministry.
The National Institute of Population and Social Security Research estimates the ratio will continue rising to reach 26 percent in 2015.
The announcement came ahead of Respect for the Aged Day on Monday.
The ratio stood at 19.2 percent in Italy in 2004, 18.0 percent in Germany in 2003, 16.2 percent in France in 2005 and 12.4 percent in the United States in 2004.