Population
The total number of people living in a census tract, and how that number has moved over one, three and five years.
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The total number of people living in a census tract, and how that number has been moving. Population is the denominator behind much of the rest of the tool and a demand signal in its own right: places that are gaining people and places that are losing them face different housing, labour and service pressures.
The figure is an American Community Survey estimate of the resident population, covering people in housing units and people in group quarters such as dormitories, nursing homes and correctional facilities. Group quarters residents have been included in ACS tabulations since 2006 (ACS Subject Definitions).
This is a survey estimate, not a headcount. It is not the decennial census count and it is not the Census Bureau's separate Population Estimates Program figure. ACS 5-year estimates are used here because they are the only ACS product published for census tracts (which estimates to use).
Metrics in this family#
Population
The current tract population, from the most recent ACS 5-year vintage.
One-year population change
Percentage change in tract population against the previous ACS 5-year vintage.
Three-year population change
Total percentage change in tract population over three years.
Three-year growth rate
The same three-year movement expressed as a compound annual growth rate, so it can be compared against annualised growth figures elsewhere.
Average annual population change, five years
The average of the annual population changes across a five-year span, in people.
Average annual population change, five years, percent
The same five-year average expressed in percentage terms, so tracts of different sizes are comparable.
Considerations#
ACS 5-year estimates describe a five-year period, not a year. Every window offered here is shorter than that, so all of them compare periods that share years — and the Bureau's guidance is "do not compare overlapping datasets" (Comparing ACS Data). We publish them because the ACS is the only source of tract-level population change, and a smoothed direction is worth having. Read them as that: rolling readings rather than independent annual counts, damped in movement, with turning points appearing later than they occurred. None of them is a measurement of change between two separate periods.
The Bureau controls the group quarters sample at the state level only, and warns that "for lower levels of geography, particularly when there are relatively few GQs in a geographic area, the ACS estimate of the GQ population may vary from the count" from the census. Tracts containing a prison, a large dormitory or a nursing home can therefore show population movement that reflects sampling rather than migration.
Census tract boundaries were redrawn for the 2020 census, and tracts are also split or merged between censuses as they grow. Estimates published on earlier boundaries are carried onto current ones before use — see geography.
Coverage runs through the most recent ACS 5-year release. Publication lags the present, and 5-year estimates are the least current of the ACS products by design.
Every ACS estimate carries a margin of error, published by the Bureau alongside the estimate; margins are widest for small tracts.
References#
- 1ACS Subject Definitionshttps://www2.census.gov/programs-surveys/acs/tech_docs/subject_definitions/2024_ACSSubjectDefinitions.pdf
- 2Using 1-Year or 5-Year American Community Survey Datahttps://www.census.gov/programs-surveys/acs/guidance/estimates.html
- 3Comparing ACS Datahttps://www.census.gov/programs-surveys/acs/guidance/comparing-acs-data.html