To determine the most expensive ZIP code to buy a home in every state, 24/7 Wall St. reviewed five-year estimates of median owner-occupied home values from the U.S. Census Bureau’s 2019 American Community Survey.
We used ZIP Code Tabulation Areas — a census geography type which defines areal representations of United States Postal Service ZIP codes (USPS ZIP codes do not define geographic boundaries but instead are a network of mail delivery routes in a service area). We refer to Census ZCTAs as ZIP codes.
Of the 33,120 ZIP codes the Census publishes data for, 32,936 had boundaries that fell within one of the 50 states, while the rest were in the District of Columbia or Puerto Rico.
ZIP codes were excluded if owner-occupied median home values were not available in the 2019 ACS, if there were fewer than 1,000 housing units, or if the sampling error associated with a ZIP code’s data was deemed too high.
The sampling error was defined as too high if the coefficient of variation — a statistical assessment of how reliable an estimate is — for a ZIP code’s owner-occupied median home value was above 15% and greater than two standard deviations above the mean CV for all ZIP codes’ owner-occupied median home values. We similarly excluded ZIP codes that had a sampling error too high for their population, using the same definition.
The remaining 17,788 places were ranked within their state based on their owner-occupied median home values. To break ties, we used median monthly housing costs with a mortgage.
In a few cases, median home values were above the upper boundary for which the U.S. Census publishes more precise estimates and instead publishes the boundary ($2,000,000+). To break ties for these areas, we used two proxies: median household income, as areas with higher incomes are correlated with higher home values, and total housing units, as a lower number of housing units implies a smaller supply of homes available if a purchaser wished to live within a given area.
Additional information on median monthly housing costs with a mortgage, the share of owner-occupied housing units that have a mortgage, rates of homeownership, and median household income are also five-year estimates from the 2019 ACS.