The question that I first asked was, why was progress . . . speeding up over time? It arises because of this special characteristic of an idea, which is if [a million people try] to discover something, if any one person finds it, everybody can use the idea.

After learning that he was one of two recipients of the 2018 Nobel Memorial Prize in Economic Sciences, as quoted in "Two Top U.S. Economists Win Nobel for Work on Growth and Climate: Research of William D. Nordhaus and Paul M. Romer has had immense impact on global policy making, the Academy says" The Wall Street Journal. October 8, 2018.