Qualitative Mismatches develops the distinction between short run qualitative mismatches for individual workers and employers and long run aggregate qualitative mismatches arising from changes in the quantity demanded or supplied in a category of the labor market. Without the distinction between the two forms, a measurement of one could be mistaken for the other. The methods and data used to examine the two forms of qualitative mismatches also differ. Short run qualitative mismatches arise as a consequence of extensive job and worker variety combined with imperfect information and frictions in the labor market that require workers and employers to engage in search to establish employment. Short run qualitative mismatches are studied by examining how the labor market assigns workers to jobs through search by workers and employers, and how qualitative mismatches arise as a consequence of the strategies of workers and employers in the presence of costly search. In contrast, long run...