Samir KC is on a mission to get people thinking differently about population growth. The basic idea of predicting future population size is so simple a child could do it. The reality of getting an accurate estimate is fiendishly complex, however, requiring intimate knowledge of how factors like education and migration will affect a given region.
“It’s very easy to do statistical extrapolation,” says KC, a professor at Shanghai University. But accuracy demands local expertise: “You need to understand a lot of things, and not everything is in the data. Only local demographers that are experts in that country can give you the right inputs.”
In a paper published in PNAS last week, KC and his colleagues show how predictions of India’s population over the next century can vary widely, depending on what data gets baked into the calculations. Population data plays a crucial role in planning for healthcare, education, and infrastructure (and in the longer term, climate change), so that variability has clear real-world implications.