Health insurance mergers have hit the headlines recently. Aetna and Humana led off by announcing their merger, followed by the agreement by Cigna to be purchased by Anthem. To some, the most notable outcome of these mergers is that they yield two very large insurers, and leave the U.S. with three large health insurers with annual revenues in the $150 billion range. In this populist, “big is bad” era there are already calls for the Justice Department to step in and prevent the mergers. Let’s think this through step by step.