Data Methodology
ZipSocio aggregates public records from the U.S. Census Bureau. Here is a breakdown of how the data is collected, defined, and calculated.
1. Data Sources
The primary source of demographics is the **U.S. Census Bureau American Community Survey (ACS)** 5-Year Estimates. We utilize 5-year estimates rather than 1-year estimates because they provide a larger sample size, which is critical for maintaining low margins of error when looking at small geographic boundaries like ZIP codes (specifically Census Zip Code Tabulation Areas, or ZCTAs).
Specifically, the current version of the site uses the **2018–2022 ACS 5-Year dataset**.
2. Geographic Definitions
The U.S. Census Bureau does not query data by mailing ZIP codes. Instead, they define **Zip Code Tabulation Areas (ZCTAs)**, which are generalized areal representations of United States Postal Service (USPS) ZIP code service areas. In over 98% of cases, ZCTAs match postal ZIP codes exactly.
Counties and state profiles are aggregated directly by their Federal Information Processing Series (FIPS) codes to ensure geographic precision.
3. Variable Definitions
Median Household Income
The median income of all households in the region. A household includes all people who occupy a housing unit as their usual place of residence. Figures are represented in inflation-adjusted dollars corresponding to the ending year of the survey.
Median Home Value & Gross Rent
Home values represent the owner's estimate of what the property would sell for. Median Gross Rent represents the contract rent plus the estimated average monthly cost of utilities if paid by the renter.
Unemployment Rate
Calculated as the percentage of the civilian labor force (people 16 years and older who are working or actively seeking work) that is currently unemployed. It excludes active military personnel and people not looking for work (e.g. retirees, students).
Bachelor's Degree Rate
The percentage of the population aged 25 years and older who have completed a bachelor's degree or higher educational degree (including master's, professional, or doctorate degrees).
4. Neighboring ZIP calculations
To display neighboring ZIP codes, ZipSocio calculates distance using the coordinates (latitude and longitude) of each ZIP code's geographic centroid.
Haversine Formula:
d = 2 * r * arcsin(sqrt(sin²(Δlat/2) + cos(lat1) * cos(lat2) * sin²(Δlon/2)))
Where `r` is the Earth's radius (approx. 3,958.8 miles), `Δlat` and `Δlon` are the difference in radians between the coordinates. We filter and display the top 8 closest neighboring ZIP codes.