In a National Bureau of Economic Research (NBER) paper, Blair and Chung find that occupational licensing reduces labor supply significantly. I had expected that occupational licensing would be worse for blacks than for whites because it imposes an additional locus of discrimination, but that effect seems to be opposed by a certification effect (the license helps black workers to overcome statistical discrimination), so the net effect is not as bad for blacks as for whites:

We exploit state variation in licensing laws to study the effect of licensing on occupational choice using a boundary discontinuity design. We find that licensing reduces equilibrium labor supply by an average of 17%-27%. The negative labor supply effects of licensing appear to be strongest for white workers and comparatively weaker for black workers.

An Institute for Justice report by Morris M. Kleiner, one of the leading authorities on occupational licensing, and Evgeny S. Vorotnikov attempts to calculate the net loss to the US economy from occupational licensing and concludes that when all costs are considered, it is on the order of $200 billion annually:

In preventing people from working in the occupations for which they are best suited, licensing misallocates people’s human capital. In forcing people to fulfill burdensome licensing requirements that do not raise quality, licensing misallocates people’s human capital, money and time. And with its promise of economic returns over and above what can be had absent licensing, licensing encourages occupational practitioners and their occupational associations to invest resources in rent-seeking instead of more productive activity. Taking these misallocated resources into account, we find potential costs to the economy that far exceed those from deadweight losses and that likely provide a more complete picture of the extent to which licensing reduces economic activity. …we find licensing costs the American economy $197.3 billion in misallocated resources.

This article was reprinted with permission from Marginal Revolution.