Pré-publication, Document de travail: After 1850, mortality began its long-term fall in most industrialized countries, a process that has been linked to rising incomes and improved water infrastructure. The problem, however, is that these contribution are jointly determined and feedback into each other. Here we estimate their impact using a longitudinal data set on mortality and income for each of Paris' 80 neighborhoods. Income and sanitation both contributed to the decrease in mortality, a standard deviation increase in either variable produces a two years gain in life expectancy. These results give insights on the determinants of the health transition but also on the long-term evolution of health inequality.