Who leaves the Oregon medical insurance pool when premiums increase?

The Oregon Medical Insurance Pool (OMIP) provides coverage for individuals unable to obtain insurance elsewhere. When premiums increased by 16.5% on January 1, 2006, 6% of enrollees discontinued coverage, creating a natural experiment to examine factors associated with disenrollment. Using a retrospective cohort of 10,586 members, we analyzed whether chronic medical conditions or income predicted discontinuation. Logistic regression showed that four conditions—alcohol use, cancer, neurological disorders, and pregnancy—were unexpectedly associated with higher odds of leaving OMIP, while income showed no significant effect. Higher premiums and shorter enrollment duration also predicted disenrollment. Findings highlight the need to understand why certain medically vulnerable groups exit high‑risk insurance pools after cost increases and how these programs might better retain enrollees.