The U.S. population in 2020 was older and had fewer children under age 5 than in 2010 or 2000, according to the 2020 Census Demographic and Housing Characteristics (DHC) data released today.
The baby boom generation (born 1946-1964) and millennials (born 1982-2000) — the two largest U.S. cohorts in 2020 — both continued to age over the past two decades. At the same time, smaller cohorts of children were born from 2010 to 2020.
The 2020 Census DHC data allows us to examine the age and sex composition of the nation and smaller geographies such as states, counties, metropolitan areas and micropolitan areas. It also shows that the age and sex compositions of different geographies do not always follow the same pattern of change over time.
While the population pyramid for the United States tells us about the nation, sex and age composition can vary significantly at the state, county, metropolitan, and micropolitan levels.
An effective way to visualize these changes is through population pyramids (Figure 1). The area of each pyramid reflects the overall size of the population while its shape illustrates the population’s age and sex distribution.
The youngest ages are reflected at the bottom of the figure; middle age groups fill its center; and the oldest ages taper to a point at the top. The number of males (on the left) and females (on the right) are shown by years of age, so a lopsided pyramid reflects more male or female births, migration into or out of a population and different life spans of men and women.