Fertility and Wars: The Case of World War I in France†

During World War I, the birth rate in France fell by 50 percent. Why? I build a model of fertility choices where the war implies a positive probability that a wife remains alone, a partially-compensated loss of a husband’s income, and a temporary decline in productivity followed by faster growth. I calibrate the model’s key parameters using pre-war data. I find that it accounts for 91 percent of the decline of the birth rate. The main determinant of this result is the loss of expected income associated with the risk that a wife remains alone. (JEL D74, J13, J24, N33, N34, N44) During the First World War (1914–1918) the birth rate in France declined by about 50 percent.1 The resulting deficit in births is estimated to be 1.4 million, which is equal to the estimated loss of French lives due to the war.2 It follows that the decline of the birth rate doubled the already large demographic impact of the war, and its effect on the French demography was noticeable well into the twentieth century. I offer a theory to account for this phenomenon. I develop a model that builds upon Greenwood, Seshadri, and Vandenbroucke (2005). The unit of analysis is a finitely-lived household made of adults and chil-dren. The household derives utility from consumption as well as from the number of children it chooses to have. However, children are costly. They require that the wife devotes a fixed fraction of her productive time to them as long as they remain in the household. In this model, the war matters because the (likely) death of a husband is a pure, negative (expected) income shock. Since children are normal goods, the war negatively affects births. I propose a quantitative exercise consisting of two steps. First, I calibrate the model to fit the time series of the French birth rate from 1800 until the eve of World War I. Second, I use the calibrated model to evaluate the effects of the war on births. I model the war as a change in the environment facing a household along thre