The California Simulation of Insurance Markets (CalSIM) model was developed by the UC Berkeley Center for Labor Research and Education and the UCLA Center for Health Policy Research to estimate the impacts of the Affordable Care Act on employer decisions to offer insurance coverage and individual decisions to obtain coverage in California. The model was funded by The California Endowment. The report highlights that Medi-Cal expansion under the Affordable Care Act will result in a significant increase in coverage with minimal cost to the state. The authors would like to thank several individuals for their involvement in developing CalSIM and preparing the report.