I agree with this. I guess you already believe they follow a bell curve.Then from your former comment you also believe it's worth it to lose many PhDs that don't contribute to also lose the few that do.

I guess the conflict is my value judgement that it's good to keep PhDs that don't contribute if it allows US to keep the ones that do contribute. I believe so for 2 reasons.

- Distinguishing between contributors and non contributors at scale is difficult.

- the value of research can be large from a few contributors.