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

During World War I (1914--1918) the birth rates of countries such as France, Germany, the U.K., Belgium and Italy fell by almost 50%. In France, where the population was 40 millions in 1914, the deficit of births is estimated at 1.4 millions over 4 years while military losses are estimated at 1.4 millions too. Thus, the fertility decline doubled the demographic impact of the war. Why did fertility decline so much? The conventional wisdom is that fertility fell below its optimal level because of the absence of men gone to war. I challenge this view using the case of France. I construct a model of optimal fertility choice where a household in its childbearing years during the war faces three shocks: (i) an increased probability that its wife remains alone after the war; (ii) a partially-compensated loss of its husband's income; and (iii) a decline in labor productivity. I calibrate the model's parameters to the time series of fertility before the war and use military casualties and income data to calibrate the shocks representing the war. The model over-predicts the fertility decline by 10% even though it does not feature any physical separations of couples. It also over-predicts the increase in fertility after the war, and generates a temporary increase in the age at birth as observed in the French data.