Household Average Size by Zip Code (ZCTA5) — Illinois

NOTE: Gray indicates insufficient data or a suppressed estimate.

The Chicago metropolitan area in northeastern Illinois displays stark internal contrasts, with suburban zip codes reaching household sizes above 3.0–3.5 persons (visible as yellow-green clusters) while dense urban cores within the city drop to 1.5–2.0 persons. Central and southern Illinois generally trend toward moderate household sizes of 2.2–2.8, though scattered rural zip codes—particularly in the western border region and near the southern tip—dip notably lower, likely reflecting aging populations and college towns. The highest household averages concentrate in outer suburban rings of the Chicagoland area, consistent with family-oriented communities in DuPage, Will, and Lake counties.

Data: U.S. Census Bureau, 2023 ACS

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