The Statistical Study of Human Populations

A pen and a 2020 United States Census form, with an American flag as the background.

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Demography is the statistical study of human populations. It includes the study of the size, structure, and distributions of different populations and changes in them in response to birth, migration, aging, and death. It also includes the analysis of the relationships between economic, social, cultural, and biological processes influencing a population. The field of sociology draws on huge bodies of data generated by a variety of sources, including the U.S. Census Bureau.

Key Takeaways: Demography

  • Demography involves the study of human populations, including how populations change over time.
  • Demographic data can be used by governments, academic researchers, and businesses.
  • One of the most well-known examples of a demographic survey is the U.S. Census, which measures the U.S. population and is used to determine political representation as well as how funds are spent.

Who Uses Demographic Data?

Demography is widely used for various purposes and can encompass small, targeted populations or mass populations. Governments use demography for political observations, scientists use demography for research purposes, and businesses use demography for the purpose of advertising.

What Do Demographers Measure?

Statistical concepts essential to demography include birth rate, death rate, infant mortality rate, fertility rate, and life expectancy. These concepts can be further broken down into more specific data, such as the ratio of men to women and the life expectancy of each gender. A census helps provide much of this information, in addition to vital statistic records. In some studies, the demography of an area is expanded to include education, income, the structure of the family unit, housing, race or ethnicity, and religion. The information gathered and studied for a demographic overview of a population depends on the party utilizing the information.

Example: The U.S. Census

In the United States, one of the best-known examples of demography is the U.S. Census. Every 10 years, each household is sent a survey containing questions about each household member's age, race, and gender, as well as information about how each household member is related. In addition to the Census, the American Community Survey is sent to a randomly chosen subset of Americans each year, in order to gather additional information (such as occupational status and education, for example). Responding to the Census (and to the American Community Survey, if one's household has been selected) is legally required, but there are policies in place to protect respondents' privacy.

Census data is used by the federal government to determine how many members of the House of Representatives each state has, and it can impact how federal funds are spent. Additionally, many researchers analyze Census and American Community Survey data, which is known as secondary data analysis. Conducting secondary data analysis allows researchers to study demography even if their research group does not have the resources to collect its own demographic data.

Example: Are Women Waiting Longer to Have Children?

As an example of how demographic data can be used by researchers, consider a 2018 report from the New York Times that looked at whether women are waiting longer to have children. Researcher Caitlin Myers analyzed National Center for Health Statistics data in order to determine when women had their first child, and whether this varied by geographic region.

In general, women waited longer to have children: the average age that women had their first child increased from 1980 to 2016. However, there were important differences depending on geographic location and education level. For example, in 2016, the average new mother in San Francisco County in California was 31.9 years old, while the average new mother in Todd County in South Dakota was 19.9 years old. Additionally, new mothers with a college degree tended to be older (the average age was 30.3 years old) than new mothers without college degrees (an average of 23.8 years old)

From the U.S. Census and vital statistics gathered using a wide variety of sources, sociologists can create a picture of the U.S. population – who we are, how we are changing, and even who we will be in the future.