Hannah Neprash: If I’m sure about anything in this world, it’s that expanding health insurance coverage will increase the total quantity of health care consumed, like Kate said! So that means M4A would need to dramatically reduce the price we pay for care, in order to rein in spending. That’s not out of the question; we know there’s tremendous variation within commercial insurance prices that doesn’t necessarily reflect higher quality. But it could raise concerns about access to care.

Brian Blase: No. Economics 101 says that increasing the demand without doing anything about the supply will put upward pressure on prices. The government can force prices below market-clearing levels, but that would lead to access problems for patients and complaints from politically powerful hospitals and providers. Also, Medicare rates are set through a political process with a bureaucracy subject to intense pressure. Unsurprisingly, Medicare overpays for certain services and procedures, and underpays for others. A single-payer program would likely lead to more wasteful health care expenditures, since it would further reduce market signals about what is valuable and what is not. Innovation and disruption represent the best way to lower costs without harming quality of care, and an even bigger Medicare-style bureaucracy would favor the status quo over more innovative ways of delivering care.