A growth model with endogenous innovation and accumulation of high-tech and low-tech human capital is developed. The model accounts for a recently established fact about human capital composition, which stated that \the richest countries are investing proportionally less than middle income...

Research and Development (R&D) endogenous growth models predict and most evidence show that investment in R&D increase with economic development. We consider the type of human capital mainly used in research labs and show that the richest countries are investing proportionally less than middle...