Looking into the Black Box: A Survey of the Matching Function

This paper surveys the microfoundations, empirical evidence, and estimation issues underlying the aggregate matching function. There is no consensus yet on microfoundations but one is emerging on estimation. An aggregate, constant returns, Cobb-Douglas matching function with hires as a function of vacancies and unemployment has been successfully estimated for several countries. Recent work has utilized disaggregated data to go beyond aggregate estimates, with many refinements and suggestions for future research. The paper discusses spatial aggregation issues, and implications of on-the-job search and of the timing of stocks and flows for estimated matching functions.