Reader Irwin Baker, of Grand Rapids, MI, has written us with a valuable citation of source material, used by Richard Baehr in this article.

Just a quibble: Since you are a stickler about Mr. Krugman's sources, I'd thought I'd let you know that the basis of your joke — 'When Krugman left MIT for Princeton I believed he thereby improved the economics faculties at both schools.' — is most often attributed to Will Rogers, speaking about moving from Oklahoma to California.  

I'm guessing that you've heard the same type of joke so often that you didn't know who originated it.  But I want to give credit to Will Rogers, since I believe he invented modern political humor.

Coincidentally, Will Rogers was also a columnist for the New York Times.

We are grateful for Mr. Baker's erudition, and are big fans of Will Rogers.