This paper assesses whether the most relevant R&D technologies at the roots of the new Schumpeterian theories of endogenous growth are consistent with patenting and innovation statistics. Using panel data for twelve US manufacturing industries, we estimate different systems of simultaneous equations drawn on the R&D races designed by the models of growth based on variety expansion, diminishing technological opportunities and rent protection activities. Although all the R&D technologies under examination are empirically grounded, our evidence indicates that those characterized by the increasing difficulty of innovation activities (i.e. diminishing technological opportunities) better fit US data.