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

During World War I the birth rate in France fell by 50%. 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% 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.