This article addresses a contested question in organizational behavior: whether workforce diversity — demographic or job-related — meaningfully affects job performance. The authors argue that prevailing assumptions (demographic diversity harms performance; job-related diversity helps) are largely artifacts of biased evaluation methods rather than reflections of actual performance differences. Drawing primarily on Van Dijk et al. (2012), a meta-analysis of 146 studies, the article presents evidence that subjective performance ratings — particularly from external evaluators — systematically underestimate demographically diverse teams (r = -0.06) while overestimating the value of job-related diversity (r = 0.09), biases that largely disappear under objective measurement conditions. Key findings indicate that job-related diversity offers modest advantages for complex and innovative tasks, while demographic diversity shows no significant negative effect under objective evaluation. All reported effect sizes remain small across diversity types and task categories. The article concludes that DEI programs retain value for reducing discriminatory practices and promoting equity, even in the absence of large performance differentials attributable to diversity itself. Key insights: Subjective performance ratings, especially from external evaluators, systematically bias results: demographic diversity is undervalued (r = -0.06 externally) while job-related diversity is overvalued (r = 0.09 externally), a pattern not replicated in objective measurement. Under objective performance measures, neither demographic nor job-related diversity shows a meaningful effect on performance for basic tasks, suggesting that much of the conventional wisdom on diversity and performance is measurement-driven rather than real. Educational diversity showed the highest effect size for innovative performance (r = 0.20), though this finding is based on only three papers and should be treated with caution. Practical takeaways: Organizations relying on external subjective performance ratings may be systematically disadvantaging demographically diverse teams through rater bias, a limitation that objective metrics could partially address. The absence of a large universal performance effect from diversity does not invalidate DEI programs; the article frames their value in terms of reducing discriminatory practices and ensuring equitable evaluation rather than direct performance gain.