We develop a product-differentiated model where the product space is a network defined as a set of varieties (nodes) linked by their degrees of substitutability (edges). We also locate consumers into this network, so that the location of each consumer (node) corresponds to her "ideal" variety....

We develop a model of vertical innovation in which firms incur a market entry cost and position themselves in the quality space. Once established, firms compete monopolistically in the quality space, selling to consumers with heterogeneous tastes for quality. Exogenously growing productivities...

Our new approach enriches the general additive monopolistic competition model (AMCM) - with a space of product characteristics: consumers' "ideal varieties". Unlike Hotelling, such partially localized competition involves intersecting zones of service among (continuously distributed) producers....