The timing of China‘s and India‘s demographic transitions and the implications of alternative fertility scenarios are here explored using a global economic model incorporating full demographic behavior and measures of dependency that include the working aged and those of working age who do not work. The results show that, while the path of total dependency in China will be comparatively flat, the positive contribution of declining youth dependency to real per capita income will not be offset by rising aged dependency until beyond 2030. India‘s dependency ratio declines more sharply. Its higher initial fertility contributes positively to growth in GDP while weakening that in its real per capita income. Yet, so long as fertility continues to decline the latter negative effect will be partially offset by a demographic dividend worth at least five per cent of its 2000 real per capita income over more than three decades.