We evaluate...the impacts of the Affordable Care Act (ACA) on insurance coverage in California.

The UCLA Center for Health Policy Research’s Health Economics and Evaluation Research (HEER) Program, in partnership with the UC Berkeley Labor Center, created the California Simulation of Insurance Markets (CalSIM), a micro-simulation model to evaluate how the Affordable Care Act (ACA) and other health reform proposals might impact health insurance enrollment in California.

Specifically, CalSIM helps California policymakers, advocates, and stakeholders project the impacts of the ACA and other proposed reforms on eligibility and enrollment in Medi-Cal, insurance through Covered California, and employer-based coverage, and who remains uninsured.

Recently the model has been used to estimate the impact of state-based reforms to expand subsidies, reinstate the “individual mandate,” and expand eligibility for Medi-Cal coverage for undocumented young adults. CalSIM uses a wide range of official data sources, including the California Health Interview Survey (CHIS).

Projections from CalSIM


more Californians would be insured if the proposal to expand Medi-Cal to all low-income residents ages 26–49 regardless of immigration status Medi-Cal occurred

2.3 million

Californians under age 65 would be uninsured by 2024, if this Medi-Cal expansion is not implemented and if enhanced federal subsidies for Covered California are not extended


fewer Californians would have individual market insurance in 2023 if American Rescue Plan subsidies are not extended