Population: An Introduction to Demography

Understanding population trends is essential in tackling many of the world’s greatest challenges, among them hunger and malnutrition, poverty, climate change, and disease, including the coronavirus pandemic. Population data are a vital tool for policymakers, business leaders, scientists, and others seeking to make informed decisions on important issues.

This Population Bulletin, “Population: An Introduction to Demography,” provides a basic understanding of demography and demographic processes, including fertility, mortality, and migration, and their effects on the world. First published in 1991 as “Population: A Lively Introduction,” this newly revised edition gives readers a greater understanding of why today’s population trends matter—not just to researchers and academics but to all of us.

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Cheerful multi-ethnic friends having fun in party

Changing Race and Ethnicity Questions on the U.S. Census Form Reflect Evolving Views

Census questions about race and ethnicity have evolved over time, as have Americans’ views about racial and ethnic identification. Nearly a century ago, enumerators for the 1920 Census were instructed to identify people as “White,” “Black,” “Mulatto,” “Chinese,” “Japanese,” “American Indian,” “Filipino,” “Hindu” (Asian Indian regardless of religion), or “Other.”1 Enumerators’ personal observations, rather than individuals’ self-identification, determined most racial/ethnic classification through the 1950 Census.

The Census Bureau emphasizes that current race categories “reflect a social definition of race … not an attempt to define race biologically, anthropologically, or genetically.”2 The 2020 Census questionnaire will ask respondents to identify their race and whether they are of Hispanic origin in two separate questions. A majority of U.S. Hispanics are Hispanic and white under the federal government’s definitions, but many Hispanics do not distinguish between race and ethnicity in this way.3 In 2010, 37 percent of Hispanics marked the “Some Other Race” category to express their racial identification—for example, Mexican or Salvadoran—which for them has more meaning than the race categories on the census form (such as white, black, Asian, etc.).

To improve the accuracy of census data, Census Bureau staff tested a single question that combined the race and Hispanic ethnicity questions and allowed respondents to report more than one category (Hispanic and White, for example).4 Results from this 2015 test showed that Hispanics were significantly more likely to identify as Hispanic rather than choose the “Some Other Race” category. The White House’s Office of Management and Budget, however, has chosen to continue to use the two-part question on race and Hispanic origin for the 2020 Census.

City University of New York sociologist Richard Alba is critical of the two-question format because it categorizes “young people with mixed Hispanic and white origins only as Hispanic—and therefore ‘non-white’ in census terminology.”5 Research shows that most of these young people perceive and experience themselves as part of the white majority and are treated as such, he reports. In Alba’s view, this classification overstates the minority share of the population, ignoring the assimilation process.

How race is categorized has important political and social implications, argue Dowell Myers and Morris Levy of the University of Southern California.They measured whites’ attitudes toward demographic change after reading different randomly assigned versions of news articles describing the Census Bureau’s population projections. Whites who read an article emphasizing the decline of the white majority reported much higher levels of anxiety and anger than whites who read about the enduring white majority as a result of intermarriage and inclusive racial/ethnic identity—racial and ethnic categories that permit people to appear in more than one group. Those who read about the declining white majority were less likely to express support for immigrants or favor a hypothetical property tax increase for K-12 education than those who read about the enduring white majority.

This article is excerpted from Mark Mather et al., “What the 2020 Census Will Tell Us About a Changing America,” Population Bulletin  vol. 74, no. 1 (2019).



  1. U.S. Census Bureau, Fourteenth Census of the United States, January 1, 1920: Instructions to Enumerators (Washington, D.C.: Government Printing Office, 1919), www.census.gov/history/pdf/1920instructions.pdf.
  2. U.S. Census Bureau, Questions Planned for the 2020 Census and American Community Survey (Washington, D.C.: U.S. Census Bureau, 2018).
  3. D’Vera Cohn, “Seeking Better Data on Hispanics, Census Bureau May Change How It Asks About Race” (April, 20, 2017), www.pewresearch.org/fact-tank/2017/04/20/seeking-better-data-on-hispanics-census-bureau-may-change-how-it-asks-about-race/.
  4. Cohn, “Seeking Better Data on Hispanics, Census Bureau May Change How It Asks About Race.”
  5. Richard Alba, “There’s a Big Problem With How the Census Measures Race,” Washington Post (February 6, 2018), www.washingtonpost.com/news/monkey-cage/wp/2018/02/06/theres-a-big-problem-with-how-the-census-measures-race/?utm_term=.96c240c6289d; and Richard Alba, “What Majority-Minority Society? A Critical Analysis of the Census Bureau’s Projections of America’s Demographic Future” Socius 4, no. 1 (August 30, 2018).
  6. Dowell Myers and Morris Levy, “Racial Population Projections and Reactions to Alternative News Accounts of Growing Diversity,” Annals of the American Academy of Political and Social Sciences 677, no. 1 (2018): 215-28.
USA, Vermont, Montpelier

The U.S. Population Is Growing at the Slowest Rate Since the 1930s

The pace of U.S. population growth is slowing, according to the Census Bureau’s 2018 estimates and 2020 projections, which provide a preview of 2020 Census results.

The U.S. population has increased each decade since the first census was conducted in 1790, surpassing 50 million by 1880, 100 million by 1920, and 200 million by 1970. The 2010 Census was the first head count in which the U.S. population exceeded 300 million. However, the rate of population growth from one decade to the next has declined since 2000 (see Figure 1).

The U.S. population increased by 10 percent between 2000 and 2010 and is projected to increase by 8 percent between 2010 and 2020, from 309 million to 333 million. An 8 percent gain would be the smallest percentage increase in the U.S. population between censuses since the 1930s; the projected numerical increase of 24 million people would be the smallest gain since the 1980s. Yet, between 2010 and 2018, the U.S. population only increased by 6 percent. Unless the rate of population growth increases over the next two years, the United States may not reach the Census Bureau’s projected population size in 2020.

Figure 1. The U.S. Population is Increasing but the pace of growth is slowing

U.S. Population and Percentage Increase in Population Between Census Years, 1790 to 2060

Source: U.S. Census Bureau, decennial censuses, and vintage 2018 population estimates

Growth in the number of households has also slowed, and population growth is on track to outpace household growth this decade for the first time since the 1930s. Between 2000 and 2010, the number of households increased by 11 percent, but household growth rates declined during the Great Recession of 2007 to 2009 and the slow economic recovery that followed. Between 2010 and 2017, the number of households increased by only 3 percent. For the household growth rate to equal the Census Bureau’s projected population growth rate of 8 percent, the number of households would have to increase by almost 6 million between 2017 and 2020. This level of growth seems unlikely given that the number of households only increased by 3.3 million over the seven-year period from 2010 to 2017. If the number of households continues to increase at the current average annual rate until 2020, the total increase for the decade is more likely to be around 4.8 million, representing a growth rate of only 4 percent—less than half the rate for the 2000 to 2010 period.

In the long term, slower population and household growth could negatively affect the future U.S. economy by reducing the supply of workers, the tax base, and the demand for goods and services. This slowdown could also reduce demand for new home construction and lead to declines in home values.

Rapid Growth Continues in the South and West

Although U.S. population growth has slowed, the rate of growth has been uneven across regions and states. The most recent estimates show that the South’s population grew 9 percent between 2010 and 2018, with the West right behind at 8 percent. Conversely, the population grew just 2 percent in the Midwest and 1 percent in the Northeast. Regional and state population trends are important not only from a demographic and economic perspective, but also because they affect the balance of political power in Congress. State population totals from the 2020 Census will determine how many congressional seats each state will have over the next decade, starting in January 2023 when the 118th Congress takes office.

Florida, with an estimated 21.3 million residents, has surpassed New York (population 19.5 million) as the nation’s third-largest state behind California and Texas. Between 2010 and 2018, 19 states (plus the District of Columbia) grew faster than the national average, and all but two (North Dakota and South Dakota) were in the South and West. In nine of those states and the District, the resident population increased by more than 10 percent.

Among the states, Utah, Texas, Florida, Colorado, and North Dakota grew the fastest between 2010 and 2018. North Dakota’s rapid population gains are linked to the oil boom earlier in this decade.1 The boom, however, has shown signs of slowing in recent years: Between 2016 and 2018, the state’s population growth rate was just under 1 percent—slightly below the national average (1.3 percent) and well below the 4 percent growth rate of Idaho, Nevada, and Utah.

The population declined in three states between 2010 and 2018: Connecticut, Illinois, and West Virginia. West Virginia’s population has declined every year since 2013, while the other two states have experienced net population loss each year since 2014. In addition, Alaska, Hawaii, Louisiana, Mississippi, New York, and Wyoming had fewer residents in 2018 than in 2016.

The post-2010 demographic situation is especially bleak in Puerto Rico. Between 2010 and 2018, Puerto Rico lost more than half a million residents, or 14 percent of its 2010 population. The rate of loss in the U.S. territory is nearly six times that of West Virginia, the state with the steepest population loss. Puerto Rico’s population decline is the result of both a financial crisis that first hit the territory in 2006 and the devastation wreaked by Hurricane Maria in 2017.2

These divergent population trends since 2010 have been even more pronounced at the county level. Between 2010 and 2018, nearly one-fifth of the nation’s 3,142 counties and county equivalents grew at or above the national rate of 6 percent; 340 of these counties grew 10 percent or more (see Figure 2). In contrast, more than half of U.S. counties (about 1,650) have experienced net population loss over the same period, with roughly 550 counties losing at least 5 percent of their residents. Most of the counties in the latter group started experiencing a net loss of residents as far back as the 1940s, and many have been declining in population since before the Great Depression.

Figure 2. The Fastest Growing Counties Are Located in the South and West

County Population Change, April 1, 2010 to July 1, 2018

Source: U.S. Census Bureau, vintage 2018 population estimates.

Counties in large metropolitan areas (1 million population or more) saw the largest population gains. As a group, their populations increased 8 percent between 2010 and 2018, and nearly half of them grew faster than the national average.

In contrast, noncore counties—those located outside metropolitan and micropolitan areas—have been the biggest demographic losers since 2010.3 Noncore counties as a group had a net loss of about 2 percent of their population between 2010 and 2018. While noncore counties comprise 42 percent of all U.S. counties, they accounted for 58 percent (967 of 1,656) of the counties that lost population.

Counties with diversified economies and access to recreational activities (entertainment industries or natural amenities) have also fared much better than those dependent on agriculture or manufacturing.

This article is excerpted from Mark Mather et al., “What the 2020 Census Will Tell Us About a Changing America,” Population Bulletin 74, no. 1 (2019).


  1. Mark Mather and Beth Jarosz, “U.S. Energy Boom Fuels Population Growth in Many Rural Counties” (March 28, 2014), accessed at www.prb.org/us-oil-rich-counties/, on Feb. 22, 2019.
  2. Mary Williams Walsh, “How Puerto Rico Is Grappling With a Debt Crisis,” The New York Times, May 16, 2017, www.nytimes.com/interactive/2017/business/dealbook/puerto-rico-debt-bankruptcy.html; and Edwin Meléndez and Jennifer Hinojosa, Estimates of Post-Hurricane Maria Exodus from Puerto Rico (New York: Center for Puerto Rican Studies, 2017).
  3. Metropolitan statistical areas have at least one urbanized area of 50,000 or more residents. Micropolitan statistical areas have at least one urban cluster of at least 10,000 but less than 50,000 residents.