Gerrymandering and the Packing and Cracking of Medical Uninsurance Rates in the United States.

CONTEXT

Technological innovation and access to big data have allowed partisan gerrymandering to increase dramatically in recent redistricting cycles.

OBJECTIVE

To understand whether and how partisan gerrymandering, including "packing" and "cracking" (ie, respectively concentrating within or dividing specified social groups across political boundaries), distorts understanding of public health need when health statistics are calculated for congressional districts (CDs).

DESIGN

Cross-sectional study using 2020 CDs and nonpartisan simulated districts.

SETTING

United States, 2017-2021.

PARTICIPANTS

United States residents.

MAIN OUTCOME MEASURE

Percent with no medical insurance (uninsured), within-district variance of percent uninsured, and between-district variance of percent uninsured.

RESULTS

At the state level, states where partisan redistricting plans showed greater evidence of partisan gerrymandering were more likely to contain CDs with more extreme values of uninsurance rates than districts in states with less evidence for gerrymandering (association between z-scores for gerrymandering and between-district variation in uninsurance = 0.25 (-0.04, 0.53), P  = .10). Comparing variation in uninsurance rates for observed CDs vs nonpartisan simulated districts across all states with more than 1 CD, in analyses stratified by state gerrymander status (no gerrymander, Democratic gerrymander, and Republican gerrymander), we found evidence of particularly extreme distortion of rates in Republican gerrymandered states, whereby Republican-leaning districts tended to have lower uninsurance rates (the percentage of Republican-leaning districts that were significantly lower than nonpartisan simulated districts was 5.1 times that of Democratic-leaning districts) and Democrat-leaning districts had higher uninsurance rates (the percentage of Democrat-leaning districts that were significantly higher than nonpartisan simulated districts was 3.0 times that of Republican-leaning districts).

CONCLUSIONS

Partisan gerrymandering can affect determination of CD-level uninsurance rates and distort understanding of public health burdens.