Title: A unified theory of the evolution of international income levels
Description: "This essay develops a theory of the evolution of international income levels.  In particular, it augments the Hansen-Prescott theory of economic development with the Parente-Prescott theory of relative efficiencies and shows that the unified theory accounts for the evolution of international income levels over the last millennium.  The essence of this unified theory is that a country starts to experience sustained increases in its living standard when production efficiency reaches a critical point.  Countries reach this critical level of efficiency at different dates not because they have access to different stocks of knowledge, but rather because they differ in the amount of society-imposed constraints on the technology choices of their citizenry"--Federal Reserve Bank of Minneapolis web site.