Child labor was induced by very specific incentives, and it was easy to spot. After the ban on those labor practices, there was no competitive advantage in bein

Child labor was induced by very specific incentives, and it was easy to spot. After the ban on those labor practices, there was no competitive advantage in being the guy who openly hires children and gets slapped down. Adverse selection problems in the job market are not so tractable. When we ban discrimination against traits that are very valuable to discriminate against, the ban just isn't going to be very effective: employers will find new and more subtle ways to continue their discrimination. Bans against discrimination on race and religion were effective because employers were hurting themselves with their bad decisions, and it was hard to hide discriminatory practices. The incentives lined up to encourage a diverse workplace. As a counter-example, bans on age-based discrimination have been very ineffective. Age-based discrimination can be subtle, yet hugely profitable for employers.