This paper analyzes the transitional dynamics of an endogenous growth model with physical capital, human capital and R&D in which both human capital and innovation drives long run growth. The model suggests that the developing economy follows different stages of development. The first phase is characterized by physical capital accumulation. At the second stage, human capital accumulation represents the main engine of long run growth. The third phase is identified by an increasing variety of

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... rmediate good originating from innovation. However, innovation is not assured for poor economies. In this case, permanent support for innovation can lead a sustainable exit from poverty trap.