Fertility Rates

Technically, fertility rates refer to the number of children a woman gives birth to during her lifetime and[Page 162] typically ranges between 0 and 12, although in some cases women may have considerably more children. Demographers often use age-specific fertility rates, which depict births to women in given 5-year age categories, because women tend to have the highest fertility rates during their main childbearing years between 15 and 40 years of age. Thus, fertility rates are closely related to birth rates (i.e., the number of babies born per 1,000 people per year) and to fecundity rates (i.e., the rate at which women biologically are potentially able to have children). Fertility is the major means by which most populations increase in size (in addition to in-migration) and is the counterpart to mortality.

However, fertility is much more than just a dry statistical measure in that it encompasses a diverse and complex set of social, cultural, economic, political, and psychological phenomena that lead it to vary widely among and within societies as well as over time and space. Although there undoubtedly are some biological factors that shape fertility rates, including genetics and diets, fertility is for the most part a reflection of the circumstances that lead women to either have children or not have children. In the world today, fertility rates range from a low of 1.3 children per woman in Spain and Portugal to roughly 8.3 children per woman in Rwanda.

Traditionally, fertility rates in preindustrial societies have been very high for a variety of reasons. In many hunting and gathering societies, fertility (and women) was celebrated as a sign of nature's benevolence. In agrarian economies, children are a vital source of farm labor, helping to plant and sow crops, tending to farm animals, performing chores, carrying water and messages, and helping with younger siblings. Children are important resources for aging parents in the absence of government programs such as social security. Finally, in such societies with high infant mortality rates, high fertility rates ensure that some proportion of children will survive until adulthood. In short, high fertility rates are rational demographic responses to agrarian poverty.

As societies industrialize, fertility rates tend to decline, a process that usually occurs slowly, over several generations, and typically well after mortality rates have fallen. Essentially, industrialization and urbanization lower fertility rates because they alter the motivations to have many children and large families. The need for child labor typically declines, whereas the costs, especially as measured in terms of forgone income in a commodified labor market, rise steadily.

As women's incomes rise, either over time or comparatively within a society, the opportunity cost of having children rises accordingly, leading to lower fertility rates. Thus, national wealth and fertility rates almost always are inversely related. If fertility rates drop to the level of mortality rates, a society reaches zero population growth, a situation characteristic of most of Europe and Japan. Societies under such conditions are characterized by large numbers of the elderly, a high median age, and a relatively small number of children, all of which have dramatic implications for public services.

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