Medicare Advantage has historically cost 7 to 12 percent more than traditional Medicare, according to the Medicare Payment Advisory Commission. But to conclude that this cost difference proves that private health plans have no place in Medicare misreads the Medicare Advantage experience in an important way: It ignores the decisive role that government has played in driving up the program's costs. Medicare Advantage is only partly about reducing costs. It is also designed to increase choice for beneficiaries. And the incentives that government gives private health plans to expand choice end up undercutting efforts to save money.