Demographers have seldom been good prophets. In 1798 Thomas Malthus, the founder of modern demography, based his famous Essay on the principle of population on the fact that American experience showed that “population, when unchecked, goes on doubling itself every twenty-five years.” Malthus was right about America in the eighteenth century, but by 1820 the American birth rate had begun to fall and by 1900 American women were having only half as many children as they had when Malthus wrote. American fertility did not decline because of food shortages, which Malthus had seen as the only effective check on population growth. The decline may have had something to do with “moral restraint,” which was the other factor Malthus thought capable of curtailing population growth, but nothing Malthus wrote explains why Americans should have exercised more restraint in the nineteenth century than they had in the eighteenth. Nor were modern methods of contraception mainly responsible. Most Americans still relied on the same contraceptive techniques at the end of the nineteenth century as at the beginning, namely abstinence, withdrawal, and abortion.
American birth rates continued falling from 1900 to 1940, with the largest decline during the 1920s. By World War II almost all American demographers assumed that fertility would keep falling as long as life expectancy kept rising and urbanization continued. The “baby boom” that began after World War II was therefore a complete surprise. Everyone expected more babies in the first years after the veterans came home, but instead of falling back to its prewar level the birth rate kept rising until 1957. Whereas women who reached childbearing age in the 1920s had had an average of just over two children, those who reached childbearing age in the 1950s averaged three.
Because the rise in American birth rates between 1946 and 1957 was completely unprecedented, most demographers assumed it was temporary. But few anticipated that fertility would fall as low as it did in the 1970s. If we keep having children at our present rate, American women born after 1955 will have an average of only 1.8 children—the lowest average in American history. Casual observers often attribute this decline to the pill, but the decline began before the pill came on the market, and the pill does not seem to have been a major factor since then. Legalized abortions may have played a larger part, but since we don’t know how many abortions took place before legalization, it is hard to be sure. In any event, surveys strongly suggest that the main reason fertility has fallen is that couples want fewer children, though it is also true that they are having fewer children they don’t want. Few demographers have even tried to explain this change in preferred family size.
Richard Easterlin, an economist at the University of Pennsylvania, is the bestknown exception. He has been promoting economic explanations of changes in fertility for nearly twenty years. In Birth and fortune: The Impact of Numbers on Human Welfare he has tried…
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