To determine the most expensive zip codes, 24/7 Wall St. reviewed data provided by Attom Data Solutions, a real estate and property data provider. Zip codes were ranked based on median sales prices of condos and single family homes from the first quarter through the third quarter of 2019. Only zip codes with at least 1,000 single family homes and condos and where at least 100 of those single family homes and condos were sold in that time frame were considered. The estimated market value is determined by Attom’s automated valuation model. Data on median household income and the share of households earning $200,000 or more are five-year estimates at the zip code level for the years 2013 to 2017 from the U.S. Census Bureau’s American Community Survey.