 Although many challenges in aggregation taken up in the justice and public health literature relate to or are compounded by the way summary measures of health are constructed and deployed, even the simplest of health measures, once aggregated, raise justice concerns. Traditionally in public health, and still today, health outcomes are often measured in what are sometimes called natural units; examples include life expectancy, mortality, five-year survival, and immunization rates. These natural units are typically expressed in terms of averages, as in average life expectancy of American men, although sometimes medians or other ways of presenting the data are used. The problem is that, aggregated over a population, any of these natural measures can obscure differences within the population that are morally relevant. To continue with the example of average life expectancy of American men, focusing only on that measure obscures differences between white men and men of color, rural and urban men, and poorly and well-educated men that many view as mattering morally, and as potential injustices. Reliance on average summary measures of things like income or education can also have implications for public health ethics. To take a classic example, averaged national income data have been used as the basis for determining which countries are eligible for international philanthropic assistance in accessing lifesaving vaccines. Because this approach resulted in the withholding of global vaccine aid from middle-income countries, it was criticized as perpetuating injustices. In middle-income countries with large income inequalities, average income data obscured truly disadvantaged sub-populations who were not likely to receive the vaccine without global assistance. (Shebaya, Sutherland, Levine, and Faden 2010) One job of public health ethics is to stay attuned to the risk that averaged outcome measures and statistics can mask differences between subgroups within a population that point to unjust inequalities in need of redress.