We find that a cross-country model of economic growth successfully tracks the growth takeoffs in China and India. The major drivers of the predicted takeoffs are improved health, increased openness to trade, and a rising labor force-to-population ratio due to fertility decline. We also explore the effect of the reallocation of labor from low-productivity agriculture to the higher-productivity industry and service sectors. Including the money value of longevity improvements in a measure of full-income reduces the gap between the magnitude of China's takeoff relative to India's due to the relative stagnation in life expectancy in China since 1980. Journal of Comparative Economics 38 (1)(2010)17-33. Harvard School of Public Health, Department of Global Health and Population, 655 Huntington Avenue, Boston, MA 02115, United States; Tsinghua University, School of Public Policy and Management, Beijing, China; Oxford University, Oxford, United Kingdom. (C) 2009 Association for Comparative Economic Studies. Published by Elsevier Inc. All rights reserved.