The world’s two population giants have undergone significant, and significantly different, demographic transitions since the 1950s. The demographic dividends associated with these transitions during the first three decades of this century are examined using a global economic model that incorporates full demographic behavior and measures of dependency that reflect the actual number of workers to non-workers, rather than the number of working aged to non-working aged. While much of China‟s demographic dividend now lies in the past, alternative assumptions about future trends in fertility and labor force participation rates are used to demonstrate that China will not necessarily enter a period of “demographic taxation” for at least another decade, if not longer. In contrast with China, much of India‟s potential demographic dividend lies in waiting for the decades ahead, with the extent and duration depending critically on a range of policy choices.