While Medicare Advantage (MA) now covers over half of Medicare beneficiaries and accounts for over $350 billion in expenditures annually, there is limited understanding of how utilization and efficiency under MA compare to Medicare Fee-for-Service (FFS), especially after adjusting for enrollment differences across the two programs. Harvard and Inovalon have partnered to answer this critical question definitively using Inovalon’s unique data assets. Inovalon’s combined data tracks individuals’ pre-65 healthcare utilization under commercial insurance coverage, as well as post-65 utilization under MA or FFS coverage. Looking at a recent five-year time period, 2015 through 2019, Inovalon’s data allowed us to produce much more statistically rigorous findings than possible with conventional data sources.We found that MA has substantially lower utilization and expenditures than FFS, even after rigorously adjusting for member enrollment differences across the two programs, including baseline demographic, clinical, and social risk factors. MA enrollees have in excess of 50% fewer inpatient stays and 22% fewer emergency doctor (ED) visits. At the same time, we found that MA has comparable amounts of primary and routine care relative to FFS, with only 7% fewer primary care provider (PCP) visits and similar prescription drug utilization. Consistent with the lower utilization, we found that overall healthcare costs, in terms of price-normalized total health expenditures, are 12% lower under MA than FFS.