This paper presents the first nonparametric test whether German works councils go hand in hand with higher labor productivity or not. It distinguishes between establishments that are covered by collective bargaining or not. Results from a Kolmogorov-Smirnov test for first order stochastic dominance tend to indicate that pro-productive effects are found in firms with collective bargaining only. However, the significance level of the test statistic is higher than a usually applied critical level. This somewhat weak evidence casts doubts on the validity of results from recent parametric approaches using a regression framework that point to high positive effects of works councils on productivity.