Multifamily Home Share
The share of a tract's housing units that sit in structures containing three or more units, and its change over time.
The share of housing units in a tract that sit in structures of three or more units.
The Census Bureau collects units in structure — "also referred to as 'type of structure'" — at both occupied and vacant housing units. "A structure is a separate building that either has open spaces on all sides or is separated from other structures by dividing walls that extend from ground to roof." Counts are "for the number of housing units in structures of specified type and size, not for the number of residential buildings," and the categories "subdivid[e] the inventory into one-family homes, apartments, and mobile homes" (ACS Subject Definitions).
The Bureau publishes buildings of two or more units under the heading "2 or More Apartments," broken into structures with 2, 3 or 4, 5 to 9, 10 to 19, 20 to 49, and 50 or more apartments. This measure counts the bands from three units upward. Two-unit buildings and mobile homes are outside it.
The denominator is all housing units in the tract, occupied and vacant alike.
Metrics in this family#
Considerations#
Three units is a boundary drawn on the Bureau's published bands, not a natural break. Duplexes fall outside this measure and inside neither it nor the single-family measure, which is why the multifamily and single-family shares of a tract do not add to one.
Structure size says nothing about tenure. Multifamily buildings can be condominiums and single-family houses are frequently rented, so this is a measure of built form rather than of the rental market. For tenure, see renter share.
The share moves when units are added or removed, and also when a tract's total stock grows around an unchanged number of apartments. A falling share is not evidence that apartments were lost.
ACS 5-year windows overlap. Each vintage shares four of its five years with the vintage before it, so year-over-year movement reflects smoothed rolling estimates rather than independent annual readings. The 5-year and 10-year trends compare vintages whose windows do not overlap; the 3-year trend compares vintages sharing two years and is damped.
Census tract boundaries were redrawn for the 2020 census. Estimates published on earlier boundaries are carried onto current ones before use — see geography.
In tracts with few housing units the estimate rests on a small sample and carries a wide margin of error.
References#
- 1ACS Subject Definitionshttps://www2.census.gov/programs-surveys/acs/tech_docs/subject_definitions/2024_ACSSubjectDefinitions.pdf