Gerontological nursing is important to meet the health needs of an aging population. Due to longer life expectancy and declining fertility rates, the proportion of the population that is considered old is increasing. Between 2000 and 2050, the number of people in the world who are over age 60 is predicted increase from 605 million to 2 billion. The proportion of older adults is already high and continuing to increase in more developed countries. In 2010, seniors (aged 65 and older) made up 13% and 23% of the populations of the US and Japan, respectively. By 2050, these proportions will increase to 21% and 36%.