The proposed research will analyze the effects on age-specific mortality of a large expansion in government health insurance coverage in Costa Rica in the 1970's. A large body of research suggests that lower health care prices lead to higher health care demand, but little is known about the magnitude of any overall mortality changes as health insurance coverage increases in low-income populations around the world. This investigation will evaluate the robustness of exploiting regional variation in the timing of the new public insurance implementation in Costa Rica, paying special attention to controls for heterogeneity such as contemporaneous regional variation in income and economic development. The specific aims of the project are to (1) Gather and integrate detailed secondary data from individual death certificates, two censuses, numerous household health and employment surveys, as well as administrative records from various government agencies; (2) Develop and refine fixed effects estimates of the insurance effects on overall mortality; and (3) Explore the robustness of estimates to numerous potential sources of measurement error and unobserved heterogeneity. If the methodology is successful, future work will explore the effects on different mortality causes such as acute versus chronic conditions, to help better understand any causal role of health insurance in the epidemiological transition.