The need for boardroom diversity is well-established. Many European countries have mandated that at least 40% of directors of publicly listed companies must be women, and similar laws have been passed in several U.S. states establishing gender- or race-based quotas. And to be sure, these policies have led to substantial progress: For example, one report found that representation of women on FTSE boards has grown eightfold in the last 25 years, from 5% up to 40%. But is simply changing the composition of boards enough to ensure that diverse perspectives are actually integrated into decision making?