This paper investigates the impact of increasing life expectancy on economic growth, using the international epidemiological transition as a natural experiment. The authors exploit the wave of health innovations and improvements that began in the 1940s to construct an instrument for changes in life expectancy, referred to as "predicted mortality." They find that predicted mortality has a significant effect on changes in life expectancy starting in 1940 but not before. A 1% increase in life expectancy leads to a 1.3-1.8% increase in population, but has a smaller effect on total GDP, both initially and over a 40-year horizon. The results suggest that while global efforts to improve health conditions in less developed countries can be highly effective, they do not significantly increase per capita economic growth. The paper also discusses the implications of these findings for neoclassical growth theory and the role of diminishing returns to labor.This paper investigates the impact of increasing life expectancy on economic growth, using the international epidemiological transition as a natural experiment. The authors exploit the wave of health innovations and improvements that began in the 1940s to construct an instrument for changes in life expectancy, referred to as "predicted mortality." They find that predicted mortality has a significant effect on changes in life expectancy starting in 1940 but not before. A 1% increase in life expectancy leads to a 1.3-1.8% increase in population, but has a smaller effect on total GDP, both initially and over a 40-year horizon. The results suggest that while global efforts to improve health conditions in less developed countries can be highly effective, they do not significantly increase per capita economic growth. The paper also discusses the implications of these findings for neoclassical growth theory and the role of diminishing returns to labor.