In my first semester in the Ph.D. program at the University of Rochester (Fall 1984), I had the good fortune to be taught by Paul Romer. I took the Math for Econ course from him. In retrospect, I can see clearly what a deep thinker he was already at that time, by the way he presented convex analysis. If later I had not been enamored by William Thomson’s game theory / social choice teachings, I may well have followed Romer in studying growth for my doctoral dissertation.
In 1990, a paper that changed the way economists understand growth was published. The author was Paul Romer. This paper presented a crystal-clear model that incorporated the idea that ideas are non-rival goods (they don’t get depleted when they get used). This paper offered such a fundamental contribution to the economic theory of growth that many economists are celebrating the 25th anniversary of its publication. Here is the contribution, also crystal clear and in plain English, of Chad Jones, to this celebration.
The curious incident of DD on the Web 