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Income Inequality by ZIP Code

The gap between the richest and poorest ZIP codes reveals stark geographic income segregation across America.

## The ZIP Code Wealth Gap

In the United States, your ZIP code is one of the strongest predictors of economic opportunity. The median household income in the wealthiest ZIP codes exceeds $250,000, while some communities report medians below $15,000.

## Extremes

| Rank | ZIP Code | Location | Median Income |
|------|----------|----------|---------------|
| Highest | 94027 | Atherton, CA | $250,000+ |
| Highest | 33109 | Fisher Island, FL | $250,000+ |
| Highest | 07078 | Short Hills, NJ | $232,000 |
| Lowest | 15767 | Smicksburg, PA | $12,500 |
| Lowest | 25264 | Southside, WV | $14,200 |
| Lowest | 41822 | Jeremiah, KY | $15,100 |

*Source: ACS 5-Year Estimates, 2018-2022*

## Geographic Patterns

Income distribution follows clear geographic patterns:

- **Coastal metros** — Highest incomes cluster in suburbs of San Francisco, New York, Washington DC
- **Rural Appalachia** — Persistent poverty in parts of KY, WV, VA, TN
- **Deep South** — Lower incomes across the MS Delta, Black Belt regions
- **Native reservations** — Among the lowest median incomes nationally
- **College towns** — Often show misleadingly low medians due to student populations

## The Opportunity Atlas

Research by Raj Chetty at Harvard has shown that children's economic mobility varies dramatically by ZIP code. Growing up in a high-opportunity ZIP code increases lifetime earnings by tens of thousands of dollars.

Key findings:

- Upward mobility is highest in areas with low segregation, low inequality, and good schools
- Moving to a better ZIP before age 13 has the largest impact
- Effects persist even after controlling for family income

## Limitations

ZIP-level income data has important limitations:

- **Averages hide variation** — A ZIP can contain both mansions and public housing
- **Sample size** — Small ZIPs have wide margins of error
- **Timing** — ACS data lags current conditions by 2-3 years
- **Cost of living** — $100K in San Francisco ≠ $100K in rural Mississippi

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Frequently Asked Questions

Where can I learn more about postal code systems?
ZipFYI's Stories section features in-depth articles about postal code systems worldwide, their history, how they work, and why they matter. Topics range from the origins of ZIP codes to how modern postal systems handle millions of packages daily.
How do postal code systems evolve over time?
Postal code systems evolve to accommodate population growth, urbanization, and changes in mail volume. New codes are created when areas develop, codes may be reassigned when delivery routes change, and entire systems can be reformed (as Ireland did with Eircode in 2015).
Why are postal codes important for businesses?
Businesses use postal codes for shipping and logistics, sales tax calculation, market analysis, customer demographics, delivery zone determination, insurance underwriting, and compliance with regulations. Accurate postal codes reduce delivery failures and improve customer experience.
How do postal codes relate to demographics?
In the US, the Census Bureau links demographic data to ZIP Code Tabulation Areas (ZCTAs). This enables analysis of population, income, education, housing, and commute patterns at the postal code level. Marketers, researchers, and policy makers rely on this data extensively.
What is geocoding and how does it relate to postal codes?
Geocoding converts addresses and postal codes into geographic coordinates (latitude/longitude). It enables mapping, distance calculations, delivery routing, and spatial analysis. Postal codes serve as a common input for geocoding services because they provide approximate location data.