Sources below. Such a large part of our pay or any of it should be weighted on customer surveys. It's a scientific proven fact that ethnic workers are judged more harshly then their white collogues. There was even a negative survey that lowered someone's pay that said "rep was great but kind of hard to understand with the accent"
https://psmag.com/economics/racism-black-restaurant-waiters-service-industry-servers-get-smaller-tips-90121
https://www.cnbc.com/2021/02/05/black-restaurant-workers-received-less-in-tips-than-others-during-pandemic.html
https://www.marketwatch.com/story/do-americans-tip-people-of-color-less-money-2017-10-31
https://www.theatlantic.com/business/archive/2015/10/why-black-workers-really-do-need-to-be-twice-as-good/409276/