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...

The "spokes model" takes the name from its graphical visualisation, that resembles the spokes of a bike's wheel. It describes a market as a collection of spokes, joining at a common centre, where consumers are located. Firms may be situated at the extreme of these spokes, at the interior of the...