The Roots of Modern Sex Ratios

While most measures of female empowerment have improved with development, sex ra- tios in many countries have become increasingly male. We exploit countries’ prior history of plough-based agriculture to identify cultural variation in patriarchal norms following Boserup (1970) and Alesina, Giuliano, and Nunn (2013). Using detailed birth records from 76 countries between 1970 and 2010, we show that the cultural legacy of plough use explains a large portion of variation in modern sex ratios, and present evidence that plough countries’ male-skewed sex ratios are achieved through a mix of in-utero sex-selection, son-based stopping rules, and increased mortality suggestive of neglect or infanticide. This cultural bias intensifies with lower fertility, even when controlling for a suite of economic and historical controls, a pattern that is not found in non-plough countries.