In the U.S. labor maarket, the vacancy-unemployment ratio and unemployment react sluggishly to productivity shocks. We show that the job matching model in its standard form cannot reproduce these patterns due to excessively rapid vacancy responses. Extending the model to incorprate sunk costs for vacancy creation yields highly realistic dynamics. Creation costs induce entrant firms to smooth the adjustment of new openings following a shock, leading the stock of vacancies to react sluggishly.

In aggregate U.S. data, exogenous shocks to labor productivity induce highly persistent and hump-shaped responses to both the vacancy-unemployment ratio and employment. We show that the standard version of the Mortensen-Pissarides matching model fails to replicate this dynamic pattern due to the rapid responses of vacancies. We extend the model by introducing a sunk cost for creating new job positions, motivated by the well-known fact that worker turnover exceeds job turnover. In the matching model with sunk costs, vacancies react sluggishly to shocks, leading to highly realistic dynamics.