Between the 1880s and 1930s, apprenticeship was transformed from an institution dominated by employers to one dominated by unions. Prior to this transformation, employers leveraged their ability to hire, fire, and discipline at will by requiring apprentices to post forfeitable performance bonds. Despite their financial interest in the resolution of contract disputes, employers who withheld employees' bonds judged their own cases. Agency theory helps explain the use and abuse of bonding schemes and their role in the subsequent transformation of apprenticeship.