Adulthood

Interest in adult development and the aging experience is a relatively new area of inquiry. Throughout the first half of the twentieth century, the study of human development was largely the study of child development. Growing awareness of the dramatic global growth in the older population and rising life expectancies led to the emergence of the field of social gerontology. In 1900 people over sixty-five accounted for approximately 4 percent of the U.S. population—less than one in twenty-five. At that time, the average life expectancy (i.e., the average length of time one could expect to live if one were born that year) was forty-seven years. In 2000 adults between twenty and forty-four years of age comprised 36.9 percent of the U.S. population; adults between forty-five and sixty-four made up 22 percent; and those over the age of sixty-five represented 12.8 percent. Today, life expectancy at birth in the United States has risen to 72.5 years for men and 79.3 years for women (U.S. Census Bureau 2000a).

All world regions are experiencing an increase in the absolute and relative size of their older populations. There are, however, substantial differences in the current numbers and expected growth rates of the older population between industrialized and developing countries. For example, 15.5 percent of the population of Europe is aged sixty-five and older. In contrast, only 2.9 percent of sub-Saharan Africa's population is over age sixty-five. The less-developed regions of the world, however, are expected to show significant increases in the size of their older populations in the upcoming decades. For example, the size of the elderly population in sub-Saharan Africa is expected to jump by 50 percent, from 19.3 million to 28.9 million people between 2000 and 2015 (U.S. Census Bureau 2000b).

The democratization of the aging experience or the longevity revolution has also led to a life course revolution (Treas and Bengtson 1982; Skolnick 1991). The changes in mortality have had a profound impact on the concept of adulthood. The odyssey from youth to old age—or the concept of adulthood—can be viewed through many different lens, including chronological, biological, psychological, social, cultural, economic, and legal perspectives.