India's Demographic Dividend in the Accounts, 1991–2025: An Exact Three-Way Split of Growth in GDP per Head, the Ceiling on What Age Structure Can Still Add, and Five Asian and Latin American Comparators

Real GDP per head in India grew by 4.58% a year (log points) between 1991 and 2025. I split this growth exactly into three parts: output per worker, the employment rate of the population aged 15 and over, and the share of the population aged 15 and over. The data are World Bank WDI constant-price GDP per head, population by age, and ILO-modelled employment ratios, vintage 8 October 2026. Over the whole period output per worker supplied 3.98 points a year (87.0% of growth), the adult share 0.61 points (13.3%) and the employment rate essentially nothing (−0.01 points). The employment rate fell from 55.5% in 2000 to 47.5% in 2020 and then rose to 53.3% in 2025, so in 2019–2025 it added 1.45 points a year, about a third of growth in that period. I prove that the adult-share term equals minus the log change in one plus the child-dependency ratio, that the log split is exact while the usual sum of percentage growth rates misses an interaction term that reached 64 percentage points over 1991–2025, and that the adult-share term can add at most 27.7 log points (31.9%) to GDP per head from its 2025 level. Reaching China's 2025 adult share would add 11.6%; reaching China's 2025 employment rate would add 15.5%. The remaining dividend from age structure is therefore smaller than the gain available from employing more of the adults India already has.