Optimal Fertility During World War I
Abstract: During World War I (1914-1918) the birth rates of countries such as France, Germany, the U.K., Belgium and Italy declined by almost 50 percent. In France,
where the population was 40 millions in 1914, the decit of births is estimated
to 1.36 millions over 4 years while military losses are estimated at 1.4 millions.
In short, 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 a partially-compensated loss of its husband's income, and an increased probability that its
wife remains alone after the war. I calibrate the model's parameters to t the
fertility data over the 100 years before the war, and the probability that a wife
remains alone after the war using the casualties sustained by the French army.
The model over-predicts the fertility decline by 34% 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