Early high fertility. From the time of the first settlements to about 1820, the fertility of the American people was among the world's highest. Contemporary writers attributed this situation to the ease with which land could be acquired by individuals and with which large families could be supported. The women of completed fertility had an average of about eight children. Perhaps two-thirds of the children survived to age 20, according to life tables of fair reliability. Despite the formerly high infant mortality, there were about three times as many persons under 16 years old per white household in the United States in 1790 as in 1950. The fertility in early times was so high that computations indicate it must have created a largely native population at an early date and much of the annual population growth in the Colonial period must have been from natural increase rather than directly from a given year's net immigration. Thus, in the area that later formed the United States, the population may have been predominantly native as early as 1660.1
Although fertility was high in early times, it varied in different population groups. It was determined from a series of Colonial censuses that throughout the eighteenth century the ratio of children under 16 years old to white women 16 years old and over was much less in the largely urban population of New York County than in the largely rural population of the balance of the Colony of New York. In 1751, Benjamin Franklin cited some of the reasons for a lower fertility in urban areas than in rural areas. Ratios of young children to women in 1800 were highest in the newer areas of settlement and lowest in the longer serried areas.
Nineteenth century declines in fertility. Ratios of children under 5 years old to white women 20 to 44 years old, computed from decennial censuses, suggest that the national birth rate declined after 1810. The adjusted ratio fell from 1,358 children under 5 years old per 1,000 women 20 to 44 years old in 1810 to 1,085 by 1840, 780 by 1880, 604 by 1920, and 419 by 1940. Subsequently it increased to 587 by 1950. The bulk____________________