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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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Size and Growth Rate

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The American population nearly quadrupled during the twentieth century. The annual rate of population growth fluctuated until about 1960, when a distinctly lower growth rate ensued.
Rapidly falling death rates, massive immigration, and a "baby boom" in midcentury
caused the American population to expand at an extraordinary rate, doubling in the first half of the century and almost doubling again in the second half (see upper chart). At the same time, the world population grew by almost the same factor of four. Thus, the American population constituted about the same fraction of the world population—4.5 percent—in 2000 as it did in 1900.

Most of the decline in death rates occurred in the early part of the century, primarily among children. Immigration rates were also highest in the early part of the century. The baby boom, which lasted from 1946 to 1964, added 76 million babies to the U.S. population.

While the population increased steadily throughout the century, the annual rate of growth varied (see lower chart). The smallest increase occurred from 1918 to 1919, when more than 100,000 U.S. soldiers died during World War I (see page 206) and more than half a million Americans died from a virulent strain of influenza that swept the nation (see page 136). The growth rate slowed again after Congress enacted restrictions on immigration in 1921 and 1924. A sharp drop in birth rates during the Depression caused a significant decline in the population growth rate. Despite these variations in the growth rate, however, the U.S. population continued to increase every year—even during World War II, despite battle deaths, diminished fertility due to the deployment of millions of soldiers, and a sharp drop in immigration. Fertility rates also fell dramatically after the baby boom, but immigration helped sustain a population growth rate of about 1 percent a year through the end of the century (see pages 84 and 14).

If these trends in fertility and immigration persist, the American population will continue to grow in the early twenty-first century, although at a diminishing rate. The U.S. Census Bureau’s "middle series" projection indicates a population of 300 million in 2011.

Chapter 1 chart 1

Source Notes
Source Abbreviations

HS series A 6; SA 1999, table 2. The figure for 2000 is from “Population and Household Topics: Estimates” at (accessed August 31, 2000). Projection for 2011 is from Population Estimates Program, Population Division, “Annual Projections of the Total Resident Population” at (accessed August 18, 2000).


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