In this paper, we analyze, estimate and compare five prototypic models of innovation, from a simple learning-by-doing model to an elaborated model that includes financial, organizational and technological determinants of innovation. From the comparison of the five models we conclude that institutions - in particular the national system of innovation - and organizations matter. The importance of networks and the importance of information flows from different economic actors add to the explanatory power and gives the best model fit among all models specified. / Series: Department of Economics Working Paper Series