[jryio]

If you "drain" something the subject of the verb is what is being drained not where it is draining to.

[JumpCrisscross]

Brain drain is a noun. In the context of American research universities, it’s historically been used one way because that was the direction of the drain.

[jknoepfler]

Monopolizing talent is a zero sum game. If your tally is in the negative, you're experiencing brain drain.