On a purely actuarial basis, one might make a case for studying adults simply because there are more of them. From the 1900 and the 1960 United States Census studies, we find that 4 percent of the population in 1900 was 65 years of age and older. In 1960, 8 percent of the population was 65 years of age and older. Approximately 3 million people in 1900 were 65 years of age and older, while 12 million in 1960 were 65 years of age and older. Looking at it another way, the median or middle age in 1900 was 16 years; in 1960, it was 31 years. The life expectancy tables indicate that for 40 year old people in 1955, the prediction was for approximately 33 more years of life.