This paper develops an endogenous growth model with doubly differentiated R&D being the growth engine. The model incorporates dynamic structural change and heterogeneous knowledge spillovers. As a result, decentralized economy may exhibit non-monotonic growth paths and declining R&D productivity. Conditions on the knowledge spillover operator granting the existence of balanced growth for first-best and market economies are obtained. Different regulation tools helpful in achieving the sustainable path and their limits are studied.

This paper combines horizontal and vertical innovations to generate an endogenous growth model allowing for structural change as an endogenous phenomenon. Older technologies are continuously replaced by newer ones due to creative destruction, and new technologies appear as a result of horizontal innovations and due to the consumers' preference for variety. We assume fixed operational costs for the manufacturing sector and an endogenously defined patent price for every new technology. Every industry is profitable only for a limited period of time, making the effective time of existence of the technology endogenous and finite. We find that in such an economy endogenous structural change is the source of ongoing economic growth. Furthermore, the range of existing sectors as well as growth rates stays constant as long as the technologies are symmetric.