Abstract. Since the early 1970s, a number of authors have calculated gender wage differentials between women and men of equal productivity. This meta-study provides a new quantitative review of this vast amount of empirical literature on gender wage differentials as it concerns not only differences in methodology, data, and time periods, but also different countries. We place particular emphasis on a proper consideration of the quality of the underlying study which is done by a weighting with quality indicators. The results show that data restrictions – i.e. the limitation of the analysis to new entrants, never-marrieds, or one narrow occupation only – have the biggest impact on the resulting gender wage gap. Moreover, we are able to show what effect a misspecification of the underlying wage equation – like the frequent use of potential experience – has on the calculated gender wage gap. Over time, raw wage differentials worldwide have fallen substantially; however, most of this decrease is due to better labor market endowments of females.