Medicare's Administrative Costs

One of the "zombies" in the health-care debate that refuses to die is the notion that a Medicare-like "public plan" does/would have lower administrative costs than private health plans. It's kind of like saying that Government Motors (formerly General Motors) will out-compete Toyota and Honda because of lower administrative costs. Nevertheless, former Labor Secretary Robert Reich brought it up again in a Wall Street Journal op-ed. I challenge it here.