Potatoes, the fruit of the earth

Nathan Nunn, Nancy Qian, 5 August 2009

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How important is nutrition to economic development? Historically, development was paralleled by growth in population and urbanisation. Hence, one way to gain some insight into this question is to understand the role that nutrition played in the historical growth in population and urbanisation. Figure 1 shows that both of these measures increased dramatically during the 18th and 19th centuries.

Figure 1. Population and urbanisation over time

Source: Nunn and Qian (2009)

The traditional explanation for the rise in population is that medical advances, such as the understanding of the germ theory or the innovation of vaccinations, and improvements in public sanitation greatly decreased infant and child mortality, which in turn led to an increase in population (e.g. Preston, 1975, 1980, 1996; Cutler, Deaton and Lleras-Muney, 2005, 2006). However, in recent years, scholars such as Thomas McKeown (1976) and Robert Fogel (1984, 1987, 1994, 2004) have argued that the increase in population was mostly due to an improvement in nutrition rather than the advances in medicine or sanitation. McKeown argued that the decline in mortality began to occur well before the most important innovations such as antibiotics or vaccinations, which did not become prevalent until the 20th century, and therefore, there is scope for other factors to contribute to the rise in population. Fogel argued that since height is positively correlated with nutritional investment during childhood as well as lower mortality rates, then the observation that heights in America and the UK were increasing is evidence that nutrition was improving during this period.

If Fogel is right, then we have to ask what caused the improvements in nutrition. Certainly, improvements in agricultural technology are part of the story. During this time, a number of productivity-enhancing technologies were developed. Examples include the seed drill, the threshing machine, and the Rotherham swing plough.

In recent research, we argue that another main contributor was the discovery of New World food crops, namely, the potato (Nunn and Qian 2009). Potatoes are extremely nutritious and a very “cheap” source of calories. They produced much higher yields per acre relative to pre-existing Old World staple crops. Historical survey data from England show that if a family of four were to subsist on only one crop, it would require 66% less land if it were to plant potatoes rather than staples such as barley, wheat, or oats (Young, 1771). Potatoes are also easy to store and were popular as fodder for livestock through the winter. Therefore, cultivating potatoes also indirectly improved protein intake. The diffusion of potatoes also had a tremendous impact on nutrition in the Old World because vast land areas in Northern Europe, Asia, and high altitude areas of Africa were suitable for cultivating potatoes. Figure 2 maps suitability for potato cultivation. Yellow and brown coloured regions are suitable. Darker coloured regions are more suitable.

Figure 2. Suitability for white potato cultivation

Our results suggest that the availability of this high-yielding crop dramatically increased population and urbanisation. The introduction of potatoes can explain 22% of the rise in population and 47% of the rise in urbanisation during the 18th and 19th centuries.

References

Cutler, David M., Angus Deaton, and Adriana Lleras-Muney, “The Role of Public Health Improvements in Health Advances: The Twentieth-Century United States,” Demography, 42 (2005), 1–22.

Cutler, David M., Angus Deaton, and Adriana Lleras-Muney, “The Determinants of Mortality,” Journal of Economic Perspectives, 20 (2006), 97–120.

Fogel, Robert W., “Nutrition and the Decline in Mortality since 1700: Some Preliminary Findings,” Working Paper 1402, NBER (1984).

Fogel, Robert W, “Economic Growth, Population Theory, and Physiology: The Bearing of Long-Term Processes on the Making of Economic Policy,” American Economic Review, 84 (1994), 369–395.

Fogel, Robert W, “New Findings on Secular Trends in Nutrition and Mortality: Some Implications for Population Theory,” in Mark R. Rosenzweig and Oded Stark, eds., Handbook of Population and Family Economics (Elsevier Science, North Holland, Charlottesville, 1997), 433–481.

Fogel, Robert W, The Escape from Hunger and Premature Death, 1700-2100 (Cambridge University Press, New York, 2004).

McKeown, Thomas, The Modern Rise of Population (Academic Press, New York, 1976).

Nunn, Nathan and Qian, Nancy (2009) “The Potato’s Contribution to Population and Urbanization: Evidence from an Historical Experiment” CEPR Discussion Paper.

Preston, Samuel H., “The Changing Relation Between Mortality and Level of Economic Development,” Population Studies, 29 (1975), 231–248.

Preston, Samuel H., “Causes and Consequences of Mortality Declines in Less Developed Countries during the 20th Century,” in Richard A. Easterlin, ed., Population and Economic Change in Developing Countries (University of Chicago Press, Chicago, 1980), 289–360.

Preston, Samuel H., “American Longevity: Past, Present, and Future,” (1996), mimeo, Syracuse University.

Young, Arthur, The Farmer ’s Tour through the East of England, Volume 4 (W. Strahan, London, 1771).

Topics: Development
Tags: nutrition, Potatoes, urbanisation

Nathan Nunn
Professor of Economics, Harvard University
Academy Scholar, Harvard Academy of International and Area Studies and Assistant Professor of Development Economics, Department of Economics, Brown University.