Maybe measure - and hear me out on this one - all team members equally, factoring in their total comp. How much more productive is the team for having the individual on the team, regardless of their demographics.
Maybe - hear me out out on this one - I did and that's why they were fired.
Why measure anyone? Measuring is for the insecure. Just trust your gut, obviously you know best...
I wish I could watch the end of your career pan out for laughs. Convinced that you're still as competent as you were when you were younger, but those assholes in charge of hiring won't give you a chance.