The top 25 Medicare Advantage insurers enroll a combined 24.3 million lives, or 87.8% of the national market, according to the December 2021 update to AIS’s Directory of Health Plans. That’s up from 21.4 million lives at year-end 2020. Among the large national insurers, Centene Corp. saw staggering growth of nearly 40%, fueled by the insurer’s significant 2021 market expansion, followed by Anthem, Inc. at 30.7%. Anthem completed its acquisition of InnovaCare Health’s MMM Holdings, the largest MA organization in Puerto Rico, in July 2021. Highmark Health and Molina Healthcare also completed deals that boosted their MA presence this year. Just one insurer in the top 25, Triple-S Management Corp., saw an enrollment loss, though it was less than 1%. See the complete list in the table below.