What the research says
McKinsey's Diversity Wins reports found that companies in the top quartile for gender diversity on executive teams were 25% more likely to achieve above-average profitability. The gap for ethnic diversity was 36%. These are correlations, not causations — but the correlation is consistent across multiple years and geographies.
The innovation argument
The most robust case for diversity is the innovation argument: teams with diverse perspectives identify a wider range of problems, generate more varied solutions and are less susceptible to groupthink. This is supported by experimental research on problem-solving performance.
Where the evidence is thinner
Diverse teams that function well — where different perspectives are genuinely heard and valued — outperform. Diverse teams with poor psychological safety or inclusion culture do not necessarily outperform.
The inclusion caveat
Diversity without inclusion is a revolving door. Organisations that recruit from diverse backgrounds but do not create genuinely inclusive cultures see higher attrition from the groups they sought to recruit.