Years ago, before PCs in the office, I had a consulting project to try to reduce turnover in the customer service department for a utility in Georgia. I developed a 'weighted application blank. We got it down to two variables - you would be hired if you spent 2 or more years at your previous job, and you lived in the same residence for more than 2 years. While it did reduce turnover, it also excluded about 75% of Black applicants. We had to scrap it.
Profiling works.
Wow, that is .... stunning. Stunning that weighting those two items had such an effect, and stunning that they scrapped it even though it was working. I just want to bounce my head off a wall when I read that.