The author uses item response theory to evaluate the increasingly prominent method of measuring labor rights developed by David Kucera. The analysis shows that most of the component items in the Kucera index relate to the same latent variable, which can be construed as “the propensity to violate labor rights.” At the same time, individual country scores highlight the method’s inability to distinguish between countries known to have excellent respect for worker rights and extremely repressive countries. The final section tests the robustness of Kucera’s finding that there is no relationship between observed labor rights violations and foreign direct investment.