Shimer's puzzle is that the textbook Diamond-Mortensen-Pissarides model exhibits fluctuations in labor market variables that are an order of magnitude too small. Introducing search effort of the unemployed brings the model's predictions for these fluctuations very close to those seen in the...

Reasonably calibrated versions of the Diamond-Mortensen-Pissarides search and matching model of unemployment underpredict, by a wide margin, the volatility of vacancies, unemployment, and the vacancies-unemployment ratio - variables at the heart of this model. These shortcomings motivate two...