The demographic character of the United States and the world has changed significantly during the past 50 years. The basic composition of American society, as viewed by its age structure, increasing ethnic and linguistic diversity, and disparities in socioeconomic status creates regional patterns of demands for housing, employment, and quality of life. Not surprisingly, large-scale population shifts experienced during the past 50 years, such as the out-migration from the industrial Northeast to the Sun Belt cities in the South and West, and the movement of people from rural to suburban and urban places and to coastal areas, has exacerbated the vulnerability of many of the nation’s citizens to environmental hazards (see Chapter 6). Changes in the age structure of the American population, its racial and ethnic diversity, and patterns of socioeconomic status also provide an important context for social science research in the field.

Life expectancy has increased dramatically over the past 50 years. In 1950, for example, a person born in the United States had a life expectancy of 68 years. By 2000, that life expectancy had increased to 77 years, leading to an increasingly large portion of the population who are over the age of 65—many of them women whose life expectancy is 5.4 years longer than that of men. By the year 2020, it is expected that 20 percent of the U.S. population will be over 65. This demographic transition is common among industrialized nations, especially those that experienced a baby boom immediately after World War II, but a generation later, fewer births occur. Unlike most countries in Western Europe, the United States has maintained birth-rates near the replacement level of 2.1 children per woman of childbearing age. Despite this, the U.S. population continues to grow, largely due to immigration.

As the population ages, more demands are placed on health care services, affordable housing, and the special needs of the elderly population during disasters. The impacts of Hurricane Charley in August 2004 (see Box 2.1) illustrate how the changing age structure of Americans affects what hazards and disaster researchers study.

There is greater diversity in terms of race, ethnicity, and culture (including language) in the United States at present than at any other time in its history. In 1950, for example, the U.S. population was approximately 150 million, with 89 percent racially classified as white and 11 percent non-white. The faces of America continue to diversify, as the 2000 Census confirms: With a population of 291 million people, 80 percent were classified as white; 13 percent African American; 4 percent Asian; 1 percent American Indian and Alaska Native or Native Hawaiian and Other Pacific Islander; and 1 percent claiming to be of one or more races. Among the white population, 17 percent claim Hispanic or Latino origin (U.S. Census,

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