The Quality Ladder and Product Variety: Larger Economies May Not Grow Faster

This paper constructs an endogenous growth model that combines the quality ladder model and the variety expansion model. Firms enter an imitation race. After the imitation process, monopolistic competition prevails and a new innovation race begins. A successful firm, by inventing a higher quality product, can take over the entire market. However, the existence of a variety of products limits the price that the successful firm can charge. We show that the present model exhibits an inverted U-shape relationship between market size and growth rate. Relatively large and small economies grow slowly while medium-sized economies grow rapidly.