As California continues to work to effectively implement the Affordable Care Act (ACA), its leaders require a good understanding of what the likely impacts of the law, and ongoing revisions, will be on its residents — and the state's budget. 

To help them, the UCLA Center for Health Policy Research and the UC Berkeley Center for Labor and Research and Education created the California Simulation of Insurance Markets (CalSIM), a micro-simulation model that has been used since 2012 to estimate the impact of various elements of the ACA. CalSIM uses a wide range of official data sources, including the California Health Interview Survey (CHIS).

The UC Berkeley Labor Center and UCLA Center for Health Policy Research created the California Simulation of Insurance Markets model to help California policymakers, advocates, and stakeholders project the impacts of the Affordable Care Act (ACA) on insurance coverage in California, particularly eligibility and enrollment in Medi-Cal, insurance through Covered California, and employer-based coverage, and who remains uninsured.


Essential health care workers and frontline medical group or hospital medicine teamwork as a group of doctors and nurses joining together as physicians unified in a 3D illustration style.

To date, CalSIM has helped California’s state and local health officials, medical providers, community representatives, insurance companies, and others to understand both eligibility and likely enrollment of Californians in the Medi-Cal expansion as well as in the state’s new health insurance exchange, Covered California. Most recently, CalSIM 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.

The California Health Benefit Exchange (Covered California), The California Endowment, the Blue Shield of California Foundation, the California Health Care Foundation, the California Wellness Foundation and the California Pan-Ethnic Health Network have provided funding for the development of CalSIM and analyses.

CalSIM was developed in the Center’s Health Economics and Evaluation Research (HEER) Program under the leadership of Professor Gerald Kominski, PhD, and in collaboration with the UC Berkeley Labor Center. For more information about CalSIM, please contact:

Gerald Kominski, PhD
Senior Fellow, UCLA Center for Health Policy Research
Principal Investigator, CalSIM