Misleading advertising in duopoly

Abstract This paper builds a model of strategic misleading advertising in duopolistic markets with horizontal product differentiation and advertising externality between firms. We investigate the effects of regulating misinformation on market competition, behaviour of firms, and social welfare. We show that the degree of advertising externality and the magnitude of advertising costs are crucial for determining the welfare effects of several regulations, including prohibiting misleading advertising, educating consumers, taxing production, and taxing misleading advertising. We extend the model by introducing heterogeneous consumers, heterogeneous production costs between firms, and the degree of advertising informativeness. Our results have important policy implications for the debate regarding regulation of advertising, especially direct‐to‐consumer advertising for prescription and over‐the‐counter drugs.