Enroll America’s Methodology for Converting ZIP Code Enrollment Data Into County Data

The Office of the Assistant Secretary for Planning and Evaluation (ASPE), within the U.S. Department of Health and Human Services (HHS), released data on the number of consumers who selected marketplace plans by ZIP code for states with federally facilitated, partnership, and supported state-based marketplaces.

Enroll America converted these ASPE ZIP code enrollment data into county level data using a U.S. Department of Housing and Urban Development (HUD) and U.S. Postal Service dataset that maps ZIP codes to counties. This dataset is available on HUD’s website. 

For ZIP codes that crossed county lines, enrollment was assigned to each county in proportion to the share of all residential addresses in each county. For example, if 20 percent of residential addresses in a ZIP code were in County A and 80 percent in County B, 20 percent of all enrollments in that ZIP code were assigned to County A and 80 percent to County B.

The ASPE ZIP code enrollment data does not include enrollment information for ZIP codes with 50 or fewer enrollment for privacy reasons (this is indicated with an asterisk in the original file). For this analysis, all ZIP codes without enrollment data were assumed to have no enrollees. A total of 29,684 ZIP codes from the 36 states were included in the original dataset. Of these, 12,010 ZIP codes have at least 51 plan selections per ZIP code. ZIP codes without data account for 4 percent (208,384 plan selections) of the total 5.45 million plan selections.

The proportion of enrollment in a county as a share of total state enrollment is based on the total number of enrollments reported in the ASPE ZIP code enrollment data. This does not include enrollment in ZIP codes with 50 or fewer enrollments.

Enroll America Menu
Are you looking for affordable health insurance? GetCoveredAmerica.org