The correct answer is Increase in the 16-64 year age group of the population.
United Nations Population Fund (UNFPA): Demographic dividend means the economic growth potential as a result of shifts in a population’s age structure, especially when the share of the working-age population (15 to 64 years) is larger than the non-working-age share of the population.
India is one of the youngest countries in the world.
India has 62.5% of its population in the age group of 15-59 years which is peak working age.
This bulge in the working-age population is going to last till 2055, or 37 years from its beginning.
This transition is mainly due to a decrease in the Total Fertility Rate (number of births per woman) after the increase in life expectancy has become stable.