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.

Crises are thresholds in human history, often marking substantial transformations in societies. Crises, however, are not instants in time. They start, unfold, and develop in a process that is often traumatic for social systems, with outcomes ranging from catastrophe to complete recovery. In this article, catastrophic models are employed to understand a non-catastrophic outcome: the complete recovery that nuragic Sardinia experienced after a long crisis, caused in the first place by unsustainable strategies of territorial expansion. Starting from the premises of the ‘Tragedy of the Commons’, it is argued that the transformation of nuragic society was the best way of avoiding the constraints that the social structure imposed on the perspective of a sustainable growth. The study is based on a geostatistical analysis of a large sample of settlements, and it attempts to quantify population growth ratios for the Late Bronze Age.

We develop an overlapping-generations model of growth and the environment in relation to public policy on education. Beyond the traditional mechanisms through which knowledge, growth, and the environment interplay, we stress the role played by education in environmental awareness. Assuming first that environmental awareness is constant, we show the existence of a balanced-growth path (BGP) along which environmental quality increases continually. Then, if education enhances environmental awareness, the equilibrium properties are modified: the economy can reach a steady state or converge to an asymptotic BGP. Therefore, education does not necessarily promote sustained and sustainable growth.