Women remain significantly underrepresented in the top decision-making bodies in the private sector. Over the past few years, increasingly more European countries have introduced statutory gender quotas to combat this underrepresentation. Other European countries have instead relied on voluntary gender diversity recommendations in the national corporate governance codes. Statutory gender quotas are significantly more effective than recommendations, as a descriptive comparison of the development of the proportion of women in the highest decision-making and supervisory bodies of the largest publicly traded companies in Europe shows. Quotas are even more effective if companies are threatened with harsh sanctions such as fines or liquidation in case of noncompliance. This suggests that voluntary commitments to recommendations or legal quotas without tough sanctions are not effective methods to increase the proportion of women in top positions significantly. This should be considered when discussing quotas for other areas such as politics, science, or the media.