Economic theory suggests that occupational licensing can be a barrier to entry that restricts labor supply (Friedman, 1962; Stigler, 1971) or a signal of quality that enhances the labor market (Leland, 1979). This paper studies two types of licenses for dental assistants (DAs) in the U.S. to illustrate the competing supply-restricting and quality-signaling effects of licensing on minority workers. Specifically, I study the effects of introducing the X-ray permit, a state-issued license to perform X-ray procedures that also carries information about a DA’ s competence, against that of the entry-level license, which provides little information about a DA’ s competence. I find that the X-ray permit requirement reduces the wage gap between non-Hispanic white and minority DAs by 8 percent, presumably because it helps minority DAs secure jobs that entail X-ray procedures. In contrast, entry-level licensing does not reduce the racial wage gap. These findings suggest that licensing alleviates statistical discrimination if it reveals information about the holder’ s productivity.

经济理论表明，职业许可可以成为限制劳动力供应的进入壁垒（Friedman，1962；Stigler，1971）或提高劳动力市场的质量信号（Leland，1979）。本文研究了美国牙医助理 (DA) 的两种类型的许可证，以说明许可证对少数族裔工人的竞争性供应限制和质量信号影响。具体来说，我研究了引入 X 射线许可证的影响，这是一种国家颁发的 X 射线程序许可证，其中也包含有关 DA 能力的信息，与入门级许可证的影响相比，入门级许可证提供的信息很少DA 的能力。我发现 X 光许可证要求将非西班牙裔白人和少数族裔 DA 之间的工资差距缩小了 8%，大概是因为它帮助少数族裔 DA 获得需要 X 射线程序的工作。相比之下，入门级执照并没有减少种族工资差距。这些发现表明，如果许可揭示了有关持有者生产力的信息，则它可以减轻统计歧视。