How are you measuring EDI against business performance? What are the real benefits?

There is a wealth of understandable enthusiasm for promoting ED&I in business, morally, ethically and also, and for business this is important, commercially too. The question is, how strong is the evidence that ED&I is good for business? Where does that come from and what does it suggest? Then there are the practical ways of measuring it, how can this be done meaningfully? Can we trust organisations to say they are following ED&I? How would we know if they were or were not? ...