Vertical product differentiation and entry deterrence

I study how a potential entrant influences quality in a model of vertical product differentiation with quality-dependent production costs. With identical costs, the incumbent will always deter entry if possible, i.e., if fixed costs are high. Quality will be set at a level lower than or equal to the optimal quality under either duopoly or monopoly. Results are completely different when the entrant has substantially lower costs. They are explained by the relative location of the entrant's quality best response to the incumbent's optimal quality choice in monopoly. This sheds new light on the influence of industrial policy on market conduct.