The New Yorker Magazine routinely rejects my cartoon caption suggestions (for their weekly contest) and now it has selected to profile Paul Krugman rather than me. These slights help me to keep working on academic stuff as I seek to rise in the REPEC rankings of economists. Over the next ten years, will Kahn or Krugman write better academic stuff? As you can see, Paul knows that his opportunity cost of another QJE is high.
"But it’s been a long time—years now—since he did any serious research. Could he, still? “I’d like to get back to it,” he says. “I’m craving the chance to do some deep thinking, and I haven’t been doing a lot of that. I guess doing the really creative academic work does require a state of mind that’s hard to maintain throughout your whole life. Even Paul Samuelson—the bulk of the stuff you read from him is before he was fifty. There was an intensity of focus that I had when I was twenty-six that I won’t be able to recapture at fifty-six. You develop your habits of mind, and to a point that’s a good thing, because you learn ways to work, but it does mean that you’re less likely to come up with something really innovative. Even if I weren’t doing all this other stuff, I don’t think I’d be producing a lot of breakthrough papers. There’s crude stuff: if I do have some brilliant academic insight, what are they going to do, give me a Nobel Prize? . . . When I was younger, when I figured something out there was this sense of the heavens parting and the choirs singing that I don’t get now. And that’s life.”"
Now, in general I agree with his life-cycle view of economic research but I can name 4 Nobel Prize winning counter-examples to Krugman's point here. Think of Becker, Heckman, Stigler, and Schultz. Each of these impressive guys did big big work after the age of 60. Krugman is still a kid and has no excuses about easing off the gas pedal.