Age mix
The share of a place's residents who are children, who are prime-age adults, and who are seniors.
On this page
How a place's residents divide between three broad stages of life.
The Census Bureau publishes resident counts by sex within single years and narrow age bands, derived from each person's reported date of birth as of the survey reference date (ACS Subject Definitions). Each share here adds the male and female counts for the bands that make up one stage and divides by the total resident count for the same place and vintage.
Under-18 share covers everyone below the age of majority: the bands under 5, 5 to 9, 10 to 14 and 15 to 17. Age 25-44 share covers the four five-year bands from 25 to 44, the years in which household formation, family formation and home buying are concentrated. Age 65+ share covers every band from 65 upward, to the Bureau's open-ended 85-and-over band.
The three shares do not sum to one. The years from 18 to 24 and from 45 to 64 are in the denominator but in none of the three numerators, which is deliberate: those are the two stages whose presence says least about a neighbourhood on its own, and folding them in would blur the three that say most.
Metrics in this family#
Considerations#
Age composition describes who lives somewhere; it is not a quality judgement, and the direction a reader wants from it depends entirely on what they are looking for. The tool therefore exposes each share as its own weightable instrument rather than folding them into one "family friendly" or "retirement" number.
The under-18 share is published as a level only. Its trend was left out because in a single tract it moves mostly with a handful of births and moves, and a three-year change in it is dominated by sampling noise rather than by anything a reader would recognise as a change in the neighbourhood.
Group quarters are counted. A tract holding a university dormitory, a barracks or a nursing home carries those residents in both the numerator and the denominator, which can push one share far from what the surrounding housing would suggest.
ACS 5-year windows overlap, so each vintage shares four of its five years with the one before it and turning points appear later than they occurred. In tracts with few residents each share carries a wide margin of error.
Census tract boundaries were redrawn for the 2020 census; earlier estimates are carried onto current boundaries before use — see geography.
References#
- 1ACS Subject Definitionshttps://www2.census.gov/programs-surveys/acs/tech_docs/subject_definitions/2024_ACSSubjectDefinitions.pdf