Demographic change and the great moderation in an overlapping generations model with matching frictions

The fraction of the labor force under 35, or youth share, has been correlated with cyclical GDP volatility over the past several decades. The youth share and business cycle fluctuations were high during the 1970s. Then, as the population aged, output volatility declined. I develop an overlapping generations model featuring search frictions and productivity shocks, in which the age distribution affects cyclical volatility through two channels. First, employment for younger workers fluctuates more, creating a composition effect. Second, inexperienced workers produce less, so firms decide how many jobs to create based on the age distribution. Both this endogenous response by firms and the composition effect increase aggregate volatility when the youth share is high. The model can replicate a large portion of the Great Moderation in GDP volatility, suggesting an important role for demographics. The model also replicates unemployment rates, separation rates, and employment volatility by age group.