A centenarian is a person who lives to or beyond the age of 100 years. Because current average global life expectancies are less than 100, the term is invariably associated with longevity. A supercentenarian is a person who has lived to the age of 110 or more, something only achieved by about one in 1,000 centenarians. Even rarer is a person who has lived to age 115 – as of July 2013, there are only 30 people in recorded history who have indisputably reached this age, of whom only Misao Okawa is still currently living. In 2012, the United Nations estimated that there were 316,600 living centenarians worldwide.
The United States currently has the greatest number of known centenarians of any nation, with 53,364 according to the 2010 Census, or 17.3 per 100,000 people. In 2010, 82.8% of US centenarians were female. Japan has the second-largest number of centenarians, with an estimated 51,376 as of September 2012. Japan started recording its centenarians in 1963, at which time the number of Japanese centenarians was found to be 153. This number surpassed the 10,000 mark in 1998, 20,000 in 2003, and 40,000 in 2009. According to a 1998 United Nations demographic survey, Japan is expected to have 272,000 centenarians by 2050; other sources suggest that the number could be closer to 1 million. The incidence of centenarians in Japan was one per 3,522 people in 2008.
The total number of centenarians in the world remains uncertain. It was estimated by the Population Division of the United Nations as 23,000 in 1950, 110,000 in 1990, 150,000 in 1995, 209,000 in 2000, 324,000 in 2005 and 455,000 in 2009. However, these older estimates did not take into account the contemporary downward adjustments of national estimates made by several countries, such as the United States; thus, in 2012, the UN estimated there to be only 316,600 centenarians worldwide. The following tabulated lists estimated centenarian populations by country, including both the latest and the earliest known estimates, where available.