A colleague i know also argues that people tend to hire/promote people who look like them (subconscious bias that they prefer their own 'kind' / stemming back to tribal era etc)
This is pure, 100% anecdote, but, I remember at my first tech job, there were basically 3 teams working on different aspects of the product. I, a white male, was on a team with 3 other white males. There was another team of around 5 or 6 who were all Chinese. The last team was probably 10-15, all Indian.
All these people were damn good at their jobs, but it was rather interesting how the demographics fell.
Part of this might be nepotism and networking. Maybe we should ban those from recruitment. Can't recommend anyone anymore. Just purely blind system, maybe text or voice changer, so visuals involved...
Orchestras have blind auditions for precisely that reason, and it apparently works. It's not a perfect system, mostly because the classical music world itself has certain barriers built into it that are tough to navigate, but it certainly does have the intended effect.
