The highly masculine sex ratio ill India has increased substantially in the
twentieth century in contrast to roost other countries in the world. Compe
ting arguments alternatively posit underenumeration, highly masculine sex r
atios as birth, or excess female mortality throughout the life course as th
e factors underlying the level of the overall sex ratio; these arguments ha
ve not been resolved. Based on population projections that simulate populat
ion dynamics, our findings show that small differences in mortality at youn
g ages, persisting over al ling period, as well as a sex ration at birth of
106 males per 100 females, result in a highly masculine population sex rat
io.