From the traditional craft hiring hall to the Web site Monster.com, a multitude of institutions exist to facilitate the matching of workers with firms. The diversity of such Labor Market Intermediaries (LMIs) encompasses criminal records providers, public employment offices, labor unions,...

It has been well documented that the share of the working-age population employed in "middle-skill" occupations has been falling for some time, while the share in lower- and higher-skill jobs has been rising -- i.e. "polarization" of the labor market (e.g. Autor 2010). However, the dynamics and...