The concept of technical progress in the Solow model was made endogenous by Lucas (1990, 1993) and Paul Romer (1990, 1994). Endogeneityis from intentional investment decisions made by entrepreneursseeking to maximize profits and earn quasi-monopoly rents due to “firstmover” advantages. Thus new technology in the form of human capitalaccumulation is not a public good but a nonrival input complementaryto all other inputs. This nonrival input is only partially excludablesince in the form of R&D it yields spillover or external benefits.