In an op-ed at the Guardian, Vermont Sen. Bernie Sanders makes the case for a single-payer health care system. I wish he had spent some time discussing his state's effort to enact just such a system, but his arguments all strike the right chord anyway. A single-payer system is not perfect. No system is perfect. But it is insane that the U.S. pays twice as much as most other countries for a health care system that produces the same or worse outcomes in terms of life expectancy, infant mortality, and other obvious measures of health care achievement.