How do you measure the productivity of a college professor?

Question

preferably in economic terms.

Answer 1

1) Number of publications (books, articles)
2) Quality of publications (In many fields of study, journals are ranked by circulation and status as "the journal of record" etc. Also, many presses are understood to have top-tier series, or clear specializations in certain disciplines and subdisciplines. Oxford U Press trumps everything in many humanities disciplines, for example.)

That's how promotion and tenure committees quantify our productivity, anyway.