Insurance Markets When Firms Are Asymmetrically Informed: A Note

We examine welfare effects of the entry of a single well-informed insurance firm into a competitive insurance market. We show that the effect depends on the structure of the market. If competitive insurers rely on the standard self-selection mechanism of a menu of contracts, then the entry of a single well-informed firm which can discriminate costlessly between consumer risk types will increase welfare. In contrast, if consumers do not know their own risk type, then the introduction of a well-informed insurer may reduce welfare.