CalSIM is a model designed to estimate the impact of the Affordable Care Act on employer and individual decisions to offer and obtain insurance coverage in California. It was developed by the UC Berkeley Center for Labor Research and Education and the UCLA Center for Health Policy Research with funding from the California Endowment. The report provides an overview of the model and its data, including changes in types of coverage for Californians under age 65, coverage with the ACA by source, exchange subsidy eligible Californians under age 65, and characteristics of Californians under age 65 eligible for exchange subsidies. The report also includes information on unsubsidized exchange or individual market characteristics of Californians under age 65 with income under <400% of FPL.