A hundred years ago, economists were theorists (armchair philosophers). Now economics rests on careful statistical analysis. Robert Barro, whose textbook is used for the macroeconomic on-line course, explains that population growth rates depend on several economic, social, and religious factors. Economists examine population growth rates by country as a function of median income, education, health care, percentage of people living in cities, women’s rights, religion, and other factors. You might compare Europe (low population growth rate) vs Africa (high population growth rate) with a egression analysis.