Karl Shell (born May 10, 1938) is an American theoretical economist, specializing in macroeconomics and monetary economics.
While Shell has published academic articles on numerous topics in economics, he is primarily known for his contributions in three areas.
Between 1966 and 1973, Shell published three papers on inventive activity, increasing returns to scale, industrial organization, and economic growth.
Among others, Paul Romer cited and heavily built upon Shell's work in his seminal papers on endogenous growth theory.
[1] Sunspot equilibrium provides a model for excess market volatility, including bank runs.