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  Chapter One:

  Size and Growth Rate
  Life Expectancy
  Age Structure
  Population Drift
  Urban, Rural, Suburban
  Foreign Born
  Large Cities



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During the first half of the century, the proportion of centenarians in the population declined, but in the last two decades of the century that age group increased more than any other.
This is one of the most puzzling trends in this book. From 1900 to 1950, the proportion of the population that had attained or surpassed the age of one hundred years declined with each census. While life expectancy was increasing dramatically at younger ages, the number of centenarians per million Americans dropped from forty-six in 1900 to fifteen in 1950. One possible explanation is that the centenarians of 1900, who were born in 1800 or earlier and had much less schooling than the centenarians of 1950, were more likely to be misinformed about their own birth dates or to overestimate their ages. A second possibility is that more members of the 1900 cohort had experienced a healthy rural upbringing whose benefits lasted a lifetime. A third possible explanation is that the huge influx of young migrants and the large number of births during those years caused the total population to grow much faster than the population of centenarians, thereby effecting a decline in the number of centenarians per million population. 

The number of centenarians per million population was roughly the same in 1975 as in 1900. By 2000, however, the number had escalated to 262 per mil-lion. According to Census Bureau estimates, 72,000 centenarians were alive in 2000—enough to fill a fair-sized city. 

Unlike life expectancy, which changes from year to year, the human life span (maximum longevity) seems to have been fixed throughout history. Despite the claims made for the exceptional longevity of Russian Georgians or Bolivian mountaineers, there is no reliable record of any human surviving past the age of 122.

Chapter 1 chart 4

Source Notes
Source Abbreviations

For 1950 to 2000, see Constance A. Krach and Victoria A. Velkoff, “Centenarians in the United States,” Current Population Reports P23-199RV (1999). For 1900 to 1940, see Ira Rosenwaike, “On Measuring the Extreme Aged in the Population,” Journal of the American Statistical Association 63 (March 1968): 29–40. For the difficulties involved in enumerating centenarians, see Jacob S. Siegel and Jeffrey S. Passel, “New Estimates of the Number of Centenarians in the United States,” Journal of the American Statistical Association 71 (September 1976):559–566.


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