How Krugman Stacks Up

In 1979, a 26-year-old Paul Krugman published two of his most influential papers on trade and economic geography, both of which were cited by the Nobel committee in awarding the Princeton professor and New York Times columnist the economics prize this morning.

Two other of his most important papers (1, 2) -- if you go by peer citations -- were written in 1991 and 1995. The 80's were also littered with other influential papers, but it's now been thirteen years since Krugman published a major work:

(Source: Thomson Reuters)

And if you factor in that Krugman published more papers per year as he got older, his rate of influence per paper has also diminished:

So it's apparent that Krugman's intellectual productivity -- as far as adding to the body of economic knowledge -- peaked in his mid-to-late 20's and again in his late-30's. How does this pattern compare with other Nobel economists?

Pretty well to at least one type of laureate, according to University of Chicago's David Galeson. Krugman's output would make him what Galenson calls a "conceptual innovator". Last year, Galenson and Ohio State's Bruce Weinberg examined the typical Nobel economics winner and found that

conceptual innovators do their most important work earlier in their careers than experimental laureates....the probability that the most conceptual laureate publishes his single best work peaks at age 25 compared to the mid-50s for the most experimental laureate. Thus while experience benefits experimental innovators, newness to a field benefits conceptual innovators.

Some other conceptual laureates include Paul Samuelson and Trygve Haavelmo while experimental laureates include Robert Fogel and Ronald Coase. 

A similar 1999 study by Hendrik Van Dalen of the Netherlands implies that more conceptual innovators have been awarded Nobels than experimental innovators. Laureates'

most important and creative contributions are written between the ages of 29 and 38. The average creative age of Nobel economists is slightly below that of laureates in physics, and considerably younger than that of laureates in chemistry and medicine/biology.

The selection of Krugman as this year's laureate also confirms that the John Bates Clark Medal, awarded to an economist under 40 who has made a significant contribution to "economic thought and knowledge," serves as the best indicator of future Nobel winners. Out of the 23 Bates Clark winners including and prior to Krugman's 1991 award year, 10 winners have also given the Nobel.

All of this isn't to say that Krugman and other conceptual economists don't have anything to offer once they get older. If anything Krugman's work as a columnist and blogger shows that influential capital earned early in one's career can be wisely spent over a lifetime.

(For more on Krugman's work, Justin Fox has both great insight into Krugman's significance and a round-up of other reactions.)