Potatoes, Milk, and the Old World Population Boom

This paper explores the role of two important food sources, potatoes and milk, in explaining the large population growth experienced throughout the Old World in the 18th and 19th centuries. Nunn and Qian (2011) show that the introduction of the potato from the New World has a significant explanatory role for within country population and urbanization growth over this period. We expand on this by considering the role of milk consumption, which is hypothesized to be a complement of potatoes due to a differential composition of essential nutrients. Using a country-level measure for the suitability of milk consumption, the frequency of lactase persistence, we show that the marginal effect of potatoes on post-1700 population and urbanization growth is positively related to milk consumption. As the frequency of milk consumption approaches unity, the marginal effect of potatoes more than doubles in magnitude compared to the baseline estimate of Nunn and Qian.