Fewer Younger Adults Drives Population Loss in Some U.S. Cities

In July 2020, the population of both males and females in their 20s and 30s was considerably larger than other age groups (Figure 1).

By July 2021, although this age group was still large in the grand scheme of the population, its male and female peaks in New York County show the most marked loss of all age groups.

For example, New York County’s population declined by 6.6% from July 1, 2020-2021, but the population ages 20-34 declined by 13.6% — twice the county’s rate. 

San Francisco County in California (Figure 2) and Suffolk County in Massachusetts (Figure 3) experienced similar patterns of population change.

In San Francisco County, the percent loss in that same population group ages 20-34 was even larger, at 15.5%, compared to less than one-half that rate, 6.3%, for the county’s total population.

Suffolk County, which contains Boston, had a smaller total population loss of about 3%, but the 20-34 age group had a similarly pronounced decline of 5.7%.

Some other counties comprised of large cities, such as Pennsylvania’s Philadelphia County (city of Philadelphia) (Figure 4) and Missouri’s St. Louis city, which is its own county (Figure 5), did not experience population declines of such large magnitude, with total population losses of 1.5% and 2.4%, respectively. 

However, their populations of adults ages 20-34 had declines that were less than two percentage points higher than the declines of their total populations. This suggests that where this age group did not have as disproportionately large a decrease, the county’s total population did not fall as substantially.

Yet, relative to the U.S. population, the counties with especially large declines continued to have a large proportion of younger working-age adults in 2021 even after these population losses.

Despite the big declines, these particular counties still had a larger share of young adults than the country as a whole (Figure 6).