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15.2: Population

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    • Anonymous
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    Learning Objectives

    1. Describe the central concepts of the study of demography.
    2. Understand demographic transition theory and how it compares with the views of Thomas Malthus.
    3. Explain why some experts feel that world hunger does not result from overpopulation.
    4. Provide examples of how US history is marked by anti-immigrant prejudice.

    Population change often has weighty consequences throughout a society. As we think about population change, we usually think about and worry about population growth, but population decline is also a concern. Consider the experience of Michigan (Dzwonkowski, 2010). Like several other northern states, Michigan has lost population during the past few decades. Its birth rate has declined by 21 percent from 1990, and elementary school populations dropped as a result. Several schools lost so many students that they had to close, and others are in danger of closing. In addition, many more people have been moving out of Michigan than moving in. Because many of those moving out are young, college-educated adults, they take with them hundreds of millions of dollars in paychecks away from Michigan’s economy and tax revenue base. They also leave behind empty houses and apartments that help depress the state’s real estate market. Because of the loss of younger residents from the declining birth rate and out-migration, Michigan’s population has become older on the average. This shift means that there is now a greater percentage of residents in their older years who need state services.

    Among other consequences, then, Michigan’s population decline has affected its economy, educational system, and services for its older residents. While Michigan and other states are shrinking, states in the southern and western regions of the nation are growing, with their large cities becoming even larger. This population growth also has consequences. For example, schools become more crowded, pressuring communities to hire more teachers and either enlarge existing schools or build new ones. The population growth also strains hospitals, social services, and many other sectors of society.

    This brief discussion of US cities underscores the various problems arising from population growth and decline. These are not just American problems, as they play out across the world. The remainder of this section introduces the study of population and then examines population problems in greater depth.

  • The Study of Population

    We have commented that population change is an important source of other changes in society. The study of population is so significant that it occupies a special subfield within sociology called demography. To be more precise, demography is the study of changes in the size and composition of population. It encompasses several concepts: fertility and birth rates, mortality and death rates, and migration. Let’s look at each of these briefly.

  • Fertility and Birth Rates

    Fertility refers to the number of live births. Demographers use several measures of fertility. One measure is the crude birth rate, or the number of live births for every 1,000 people in a population in a given year. We call this a “crude” birth rate because the population component consists of the total population, not just the number of women or even the number of women of childbearing age (commonly considered 15–44 years).

    A second measure is the general fertility rate (also just called the fertility rate or birth rate), or the number of live births per 1,000 women aged 15–44 (i.e., of childbearing age). The US general fertility rate for 2010 was about 64.7 (i.e., 64.7 births per 1,000 women aged 15–44) (Sutton & Hamilton, 2011).

    A third measure is the total fertility rate, or the number of children an average woman is expected to have in her lifetime (taking into account that some women have more children and some women have fewer or no children). This measure often appears in the news media and is more easily understood by the public than either of the first two measures. In 2010, the US total fertility rate was about 1.93 (or 1,930 births for every 1,000 women) (Hamilton, Martin, & Ventura, 2011).


    Demographers use several measures of fertility. The general fertility rate refers to the number of live births per 1,000 women aged 15–44. The US general fertility rate is about 65.5.

    Daniel – Delivery – CC BY-NC-ND 2.0.

    As Figure 15.1 “US General Fertility Rate, 1920–2010” indicates, the US general fertility rate has changed a lot since 1920, dropping from 101 (per 1,000 women aged 15–44) in 1920 to 70 in 1935, during the Great Depression, before rising afterward until 1955. (Note the very sharp increase from 1945 to 1955, as the post–World War II baby boom began.) The fertility rate then fell steadily after 1960 until the 1970s but has remained rather steady since then, fluctuating only slightly between 65 and 70 per 1,000 women aged 15–44.

    Figure 15.1 US General Fertility Rate, 1920–2010


    Sources: Data from Hamilton, B. E., Martin, J. A., & Ventura, S. J. (2011). Births: Preliminary data for 2010. National Vital Statistics Reports, 60(2), 1–13; Martin, J. A., Hamilton, B. E., Sutton, P. D., Ventura, S. J., Menacker, F., Kirmeyer, S., & Mathews, T. J. (2009). Births: Final data for 2006. National Vital Statistics Reports, 57(7), 1–102; US Census Bureau. (1951). Statistical abstract of the United States: 1951. Washington, DC: US Government Printing Office.

    Fertility rates differ around the world and are especially high in poor nations (see Figure 15.2 “Crude Birth Rates around the World, 2008 (Number of Births per 1,000 Population)”). Demographers identify several reasons for these high rates (Weeks, 2012).

    Figure 15.2 Crude Birth Rates around the World, 2008 (Number of Births per 1,000 Population)


    Source: Adapted from

    First, poor nations are usually agricultural ones. In agricultural societies, children are an important economic resource, as a family will be more productive if it has more children. This means that families will ordinarily try to have as many children as possible. Second, infant and child mortality rates are high in these nations. Because parents realize that one or more of their children may die before adulthood, they have more children to make up for the anticipated deaths.

    A third reason is that many parents in low-income nations prefer sons to daughters, and, if a daughter is born, they try again for a son. Fourth, traditional gender roles are often very strong in poor nations, and these roles include the belief that women should be wives and mothers above all. With this ideology in place, it is not surprising that women will have several children. Finally, contraception is uncommon in poor nations. Without contraception, many more pregnancies and births certainly occur. For all these reasons, then, fertility is much higher in poor nations than in rich nations.


    Poor nations have higher birth rates for several reasons. One reason is the agricultural economies typical of these nations. In these economies, children are an important economic resource, and families will ordinarily try to have as many children as possible.

    Wikimedia Commons – public domain.

  • Mortality and Death Rates

    Mortality is the flip side of fertility and refers to the number of deaths. Demographers measure it with the crude death rate, the number of deaths for every 1,000 people in a population in a given year. We call this a “crude” death rate because the population component consists of the total population and does not take its age distribution into account. All things equal, a society with a higher proportion of older people should have a higher crude death rate. Demographers often calculate age-adjusted death rates that adjust for a population’s age distribution.

  • Migration

    Another important demographic concept is migration, the movement of people into and out of specific regions. Since the dawn of human history, people have migrated in search of a better life, and many have been forced to migrate by ethnic conflict or the slave trade.

    Several classifications of migration exist. When people move into a region, we call it in-migration, or immigration; when they move out of a region, we call it out-migration, or emigration. The in-migration rate is the number of people moving into a region for every 1,000 people in the region, while the out-migration rate is the number of people moving from the region for every 1,000 people. The difference between the two is the net migration rate (in-migration minus out-migration). Recalling our earlier discussion. Michigan has had a net migration of less than zero, as its out-migration has exceeded its in-migration.

    Migration can also be either domestic or international in scope. Domestic migration happens within a country’s national borders, as when retired people from the northeastern United States move to Florida or the Southwest. International migration happens across national borders. When international immigration is heavy, the effect on population growth and other aspects of national life can be significant, as can increased prejudice against the new immigrants. Domestic migration can also have a large impact. The great migration of African Americans from the South into northern cities during the first half of the twentieth century changed many aspects of those cities’ lives (Wilkerson, 2011). Meanwhile, the movement during the past few decades of northerners into the South and Southwest also had quite an impact: The housing market initially exploded, for example, and traffic increased.

  • 15.2: Population is shared under a CC BY-NC-SA 3.0 license and was authored, remixed, and/or curated by Anonymous via source content that was edited to conform to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.