Both freshwater and saltwater (for reference, these refer to geographical locations in the US: Chicago and Minnesota near lakes, and MIT, Harvard, Yale, Stanfor

Both freshwater and saltwater (for reference, these refer to geographical locations in the US: Chicago and Minnesota near lakes, and MIT, Harvard, Yale, Stanford, etc. near the coasts) claim that you can't run out of demand, in the long run. These schools differ in their analysis of the business cycle, that is the fluctuations around equilibrium output that are called booms and recessions/depressions. Saltwater economists believe that you can have too little/too much demand during booms/recessions. These are generally called "out of equilibrium" conditions. Neither group claim that in equilibrium, you can run out of demand. Source: I have a PhD in economics. EDIT: also see vezzy-fnord's answer, most "Freshwater" economists are and were some kind of Keynesian.