Platform · Glossary
ZIP code.
A delivery area defined by the U.S. Postal Service. ZIP codes were created in 1963 to optimize mail routing, not to describe communities, demographics, or housing markets. They have endured in popular use because they're memorable, but they're a poor unit for analytical work.
Why ZIP codes are weak for real estate analysis
- They aren't communities. A ZIP can span a wealthy enclave and an adjacent working-class area; the aggregate hides the contrast.
- They aren't stable. USPS occasionally splits, merges, or reroutes ZIPs as delivery volumes shift. Comparisons across years drift.
- They aren't aligned with Census or political boundaries. A ZIP can cross county or even state lines, making aggregation against other datasets messy.
- Statistical agencies don't actually publish data for ZIPs. The Census Bureau publishes data for ZCTAs (ZIP Code Tabulation Areas), which approximate ZIPs but are not the same boundaries USPS uses.
What 3Y uses instead
3Y uses census tracts as the analytical atom for most market and property work. Tracts are designed for statistical purposes — stable across time, populated to be statistically reliable, and aligned with the geographies that publishing agencies actually use. The result is more accurate, more comparable, and more honest analysis than ZIP-based aggregates can produce.