Special Report

ZIP Codes With the Worst Health Insurance Coverage in the Nation

Methodology

To determine the ZIP codes with the worst health insurance coverage in the nation, 24/7 Tempo reviewed five-year estimates of the percentage of the noninstitutionalized civilian population under 65 without health insurance 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, 32,989 had boundaries that fell within one of the 50 states or the District of Columbia.

ZIP codes were excluded if the noninstitutionalized civilian population under 65 was less than 1,000 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 under 65 uninsured rate was above 15% and greater than two standard deviations above the mean CV for all ZIP codes’ under 65 uninsured rates. We similarly excluded ZIP codes that had a sampling error too high for their under 65 noninstitutionalized civilian population, using the same definition.

We selected the under 65 age group because Americans become eligible for Medicare at age 65, and the uninsured rate for the population above this age is less than 1% nationwide. However, because the Census doesn’t publish insurance coverage estimates specifically for the under 65 age group, we aggregated the data from more granular age breakdowns. 

To ensure each aggregate estimate’s sampling error could be assessed using the definition above, we derived a margin of error for each aggregate estimate using the successive differences replication variance estimation methodology recommended and used by the U.S. Census Bureau. 

The remaining 19,556 places were ranked based on their under 65 uninsured rates. To break ties, we used the number of insured people in the same population group.

The share of the population covered by each type of insurance — Medicare, Medicaid, VA, employer, direct-purchase, and Tricare/military — are for the same cohort and are also aggregated from five-year ACS estimates. The estimates reflect people who are covered by that type of insurance alone or in combination with other types on the list. So, when a person is covered by more than one type of insurance, they are included in each group.

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