"Among the most developed countries, the fraction of the population aged 15-64 is forecast to fall from 70% to 60% over the next 50 years as working-age adults move into old age. Among the least developed countries, the working age fraction of the population is forecast to rise from 55% to 65%."

A) Calculate the effect of this change in demographics on the annual growth rate of GDP per capita in the most developed countries as well as the least developed countries. [Hint1: use the relationship covered in class between GDP per capita (Y/P), GDP per worker (Y/L), and labor force participation rate (L/P); Hint2: make use of the formula for growth rates to calculate the growth of the labor force over time]. In your answer, be clear about the assumption you have to make in order to give a precise answer to this question.

B) What is the principal cause of the increase in the working-age fraction of the population in the least developed countries?