A single employee who can prove that age was a factor in denying promotion, assignment, etc....go read it yourself...who has been discriminated against due to age can be evaluated for EEOC violations. Things like failure to provide reasonable explanation of why such moves were made or promotion or bonuses were denied or moving people to less desirable assignments...without explanation or being named BB and pot shotting employees with an article on retiring retirement the day after a layoff announcement, moving employees with more experience and seniority while keeping younger new employees with less seniority and experience...these are the things EEOC looks at. Also, poor definition of job description. Constructive discharge, retaliation. Poor training, unreasonable demands or assignments. I'm not going to go on. But...the first thing to be asked is not the ratio, it will be the criteria used to pick these forces transitions and if that cannot be explained, they are in serious trouble.
Thought this was a useful post. OP by @VSU7PtP-1uba