From Gabe Chodorow-Reich and Loukas Karabarbounis:
The flow opportunity cost of moving from unemployment to employment consists of foregone public benefits and foregone utility from non-working time relative to consumption. Using detailed microdata, administrative data, and the structure of the search and matching model with concave and non-separable preferences, we document that the opportunity cost of employment is as procyclical as, and more volatile than, the marginal product of employment. The empirically-observed cyclicality of the opportunity cost implies that unemployment volatility in search and matching models of the labor market is far smaller than that observed in the data. This result holds irrespective of the level of the opportunity cost or whether wages are set by Nash bargaining or by an alternating-offer bargaining process. We conclude that appealing to aspects of labor supply does not help search and matching models explain aggregate employment fluctuations.