We develop a model of repeated product improvements in a continuum of sectors. Each product follows a stochastic progression up a quality ladder. Progress is not uniform across sectors, so an equilibrium distribution of qualities evolves over time. But the rate of aggregate growth is constant....

Recent developments in the theory of economic growth and dynamic trade theory are reviewed and interpreted. These include growth based on economies of scale, trade with product development, and product cycles. It is argued that there is need for more work in this area in order to understand the...