According to search and matching theory, a greater availability of unemployed workers should make it easier for a firm to fill a vacancy, but more vacancies at other firms should make recruitment more difficult. Simulating a theoretical model of a firm facing perfect competition in the product market and no convex adjustment costs (standard assumptions in the search and matching literature), I find that shocks to vacancies and unemployment lead to economically significant employment responses. Simulating a more realistic model with imperfect competition in the product market and convex adjustment costs, I find small employment effects of shocks to vacancies and unemployment. In particular, shocks to the number of unemployed seem to be unimportant. Estimating an employment equation on a panel of Swedish firms, I find that neither the number of unemployed workers nor the number of vacancies in the local labor market is important for firms' employment decisions.