First published in 1997 and now in its 25th year, Michigan Health Market Review analyzes the health care payer and provider markets in the state. The reports provide a comprehensive and objective analysis of strategies and key trends for the health insurers and provider systems in Michigan. Part One presents our analysis of the health insurers, their financial performance, enrollment and market share. The data show the impact of the COVID-19 pandemic on health insurers in 2020 and also the growth of enrollment in 2020 and the first quarter of 2021. The Part Two report discusses the health systems, their financial results and their inpatient occupancy and payer mix based on 2020 data. The reports also include an extended analysis of implementation of key elements of the Affordable Care Act in the state, including Medicaid expansion, Medicare Accountable Care Organizations and developments in the individual market.