Research Brief

A History of Plough-Based Farming Leads to Fewer Girls

Modern-day gender ratios are linked to countries’ agricultural roots

Look to history and you’ll find plenty of examples of farming communities where women worked as much as — or more than — the men. But in plough-intensive societies, where cultivation and planting relied on physical strength, men were the primary farmers. Fast-forward to today, and many of those same societies have higher-than-average ratios of men to women. Is there a connection?

Researchers Alberto Alesina of Harvard University, Paola Giuliano of UCLA Anderson and Nathan Nunn of Harvard suggest there is. In a paper published in January 2018 in PLoS ONE, the authors offer evidence that traditionally plough-based societies, in countries such as China and India, long ago began placing more value on boys than girls, with direct consequences for modern-day populations. Even today, they write, these societies are more likely to practice female-selective abortion and infanticide, and to restrict family resources like access to nutritious food and health care based on a child’s gender, leading to higher infant mortality rates for girls.

The United Nations Population Fund estimates that, as a result of practices like these, in Asia and Eastern Europe about 117 million women are “missing” — because girls were killed or were never born. This is alarming, the U.N. says, not only because it reflects the persistent low status of women and girls, but also because the gender imbalance has been linked to increased sexual violence and trafficking.

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A biologically normal sex ratio ranges from 102 to 106 boys for every 100 girls, according to the U.N. China, perhaps the country best known for a gender imbalance, today has 115.9 boy births for every 100 girl births. In 2015, an aging population and shrinking workforce led the Chinese government to drop its one-child policy and instead encourage women to have more babies. But widespread reporting on the change shows that boys are still favored.

Using data from the Ethnographic Atlas and the Demographic Yearbook of the United Nations, Alesina, Giuliano and Nunn looked at 146 countries: 79 that traditionally engaged in plough agriculture, and 67 that used handheld farming tools.

In every age group, the male-to-female ratio was greater among plough-based societies, even controlling for modern variables like fertility rates and level of economic development, and ancestral characteristics like climate and settlement patterns. And the gap widened the older the children were, something potentially explained by higher female mortality rates. Among children ages 5 to 14, plough-based countries had a male-to-female ratio of 104.5, versus 101.9 for non-plough countries.

Giuliano and her colleagues emphasize that agricultural roots alone don’t determine sex ratios. Indeed, there is a large body of research assessing other potential variables, including biological factors that could influence gender at birth, and economic factors that affect how women are valued and thus how well girls are cared for early in life.

But even some of that might be traced to farming methods. Danish economist Ester Boserup suggested that the plough, introduced 5,000 years ago in Mesopotamia, is what led to a division of labor and the creation of gender norms, eventually making women less valued in society and in the workplace. Skewed gender ratios, then, could be a natural, if unsettling, outcome.

Featured Faculty

  • Paola Giuliano

    Professor of Economics; Justice Elwood Lui Endowed Term Chair in Management

About the Research

Alesina A., Giuliano P., & Nunn N. (2018). Traditional agricultural practices and the sex ratio todayPLoS ONE 13(1). doi: 10.1371/journal.pone.0190510.

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