McKinsey has studied this extensively had has repeatedly found that diversity is financially beneficial to companies. They've had at least 4 reports on the subject.
https://www.mckinsey.com/featured-insights/diversity-and-inc...
Landing page:
https://www.mckinsey.com/featured-insights/diversity-and-inc...
It's obvious why this is the case if you sit down and think about it. Echo chambers of like-minded individuals can't understand customers as well as a workforce of people who represent the diversity of those customers.
This isn't just diversity of race or gender, it's also diversity of thought and background.
Also critical and under-emphasized: the E and I in DEI, equity and inclusion. Power distance and lack of inclusion can railroad companies into giving the people with the most power the most influence on decisions, rather than giving the best ideas a chance to breathe.
In business a classic example might be "men designing women's clothing." How are you going to understand your customers if none of your employees and leadership resemble those customers? Perhaps you can figure it out and make some decent products but your competitor who has more diversity in their workforce is likely to outperform you, which is exactly what McKinsey's studies have demonstrated.
I will also point out that the only reason anyone started questioning this obviously true business concept and changing opinions into being against DEI is because the Republican Party's strategists figured out that they could appropriate and leverage the term "DEI" and attach it to the latent reactionary racism that much of the US still holds dear.
You can get away with saying "I don't like DEI" in public but if you say "I don't like black people" or "I don't think women should get hired for important roles" [1] that is obviously not acceptable, even though a large percentage of Americans feel that way. Right wing media twisted a largely innocent term into a useful dogwhistle.
[1] https://journals.sagepub.com/doi/10.1177/1532673X251369844
Not to agree or disagree, but the McKinsey has been heavily criticised as bogus. For example https://econjwatch.org/File+download/1296/GreenHandMar2024.p....
Those McKinsey/HBR studies are trash. They privilege the hypothesis, overlook the obvious ecological fallacy at play and add in a bit of a sampling bias for good measure. The fact that East Asian Economies are all booming and exporting globally with ~0 diversity and unique cultures ought to refute this notion. I'm sure there is some no true scotsman line you can play here about how the true meaning of DEI, and I would agree that the stated goals of DEI are all laudable. But in practice these initiatives often amounted to unprincipled discrimination and venal power grabs, which is why they are so widely despised.
The teams in the Manhattan project, the Apollo project, the inventors of the transistor, the guys who designed the Hoover dam, who wrote Doom, etc. etc. etc. etc. were not very diverse.
You might not like it, but this is what peak performance looks like.
They were "not very diverse" teams but actually did have minorities in them, and those ones truly deserved their positions.
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