The US currently ranks 56th internationally when it comes to infant mortality. We’re doing worse than just about every other rich country, and a bunch of non-rich ones too. Cuba, Poland, Bosnia, and Serbia are beating us, for example. Explanations for this vary*, and a new working paper by USC’s Alice Chen, MIT’s Heidi Williams, and University of Chicago’s Emily Oster provides a nice overview of them. But the paper’s most striking finding isn’t about the precise causes of the mortality gap between the US and peer countries. It’s about who bears the cost of that gap. The authors find that there’s very little difference between the US (which has 6.17 infant deaths per 100,000), Finland (3.36), and Austria (4.16) when it comes to deaths in the first month ("neonatal deaths"). The differences come when you look at months two through twelve of an infant’s first year. Then, the authors break down the mortality rates for each country by social standing. They find infants born to "mothers who are high education/occupation, married and white" in each country have basically identical mortality rates. American children of rich white moms who went to college do just as well as their Finnish counterparts. But there’s a BIG gap between less advantaged groups in each country. "Higher postneonatal mortality in the US," the authors write, "is due entirely, or almost entirely, to high mortality among less advantaged groups": (Chen, Williams, and Oster, 2014) "This postneonatal mortality disadvantage," they conclude, "is driven almost exclusively by excess inequality in the US." The paper isn’t primarily concerned with how to fix this problem, but the authors do note one promising option: home visits by nurses. "Both Finland and Austria, along with much of the rest of Europe, have policies which bring nurses or other health professionals to visit parents and infants at home," they note. Randomized trials in the United States have found similar programs reduce child abuse, neglect, and injury, though effects on mortality are less well-established. * They include differences in reporting extreme preterm births (which some countries classify as births, raising their mortality numbers, and others classify as stillbirths, lowering theirs), differences in birth weight and other health indicators at birth, and differences in care after birth. One methodological advantage of the Chen, Williams, and Oster paper is that it compares countries that use the same reporting standards for preterm births, eliminating that potential source of error.