Of all the oddities of the U.S. health care system, one stands out: we spend far more on health care per person than other industrialized nations yet have no better health outcomes. Understanding why isn't easy. A 2012 paper by the Commonwealth Fund found that among 13 industrialized countries studied, the U.S. has the highest rate of obesity, which is usually a factor in higher health care costs. Yet, the U.S. ranks far behind many other countries in our rates of citizens who smoke or are over 55, two other strong indicators of increased spending. So why is our health care spending more than 17% of our gross domestic product, far more than any other country? A central reason U.S. health care spending is so high is that hospitals and doctors charge more for their services and there's little transparency about why. There is no uniformity to the system, in which public and private insurers have separate, unrelated contracts with hospitals and doctors. The result is a tangled, confusing and largely secretive collection of forces driving health care prices higher and higher. This isn't possible in many other countries either because governments set prices for health care services or broker negotiations between coalitions of insurers and providers. Known as all-payer rate setting," insurers in these systems band together to negotiate as groups. In contrast, U.S. insurers closely guard the secrecy of their contracted prices with health care providers and negotiate individually. This is why a hospital hosting five patients for knee replacements might get paid five different amounts for the surgeries.