Demographic changes have created an urgent need. The growth in the number and proportion of older adults is unprecedented in the history of the United States. Two factors—longer life spans and aging boomers (those born between 1946 and 1964)—will combine to double the population of Americans age 65 years or older during the next 25 years to about 72 million. By 2030, older adults will account for roughly 20% of the US population.