Due to imperfect and incomplete institutions, firms have to consider the externalities they generate. The firm’s residual risk is not restricted to shareholders. We propose to define stakeholders as economic actors who simultaneously hold a resource used by the firm and are exposed to the risk of the firm’s activity. Risk exposure is a dynamic concept that results from institutions and corporate governance mechanisms. This definition has normative, instrumental and positive implications since it helps to define and to identify the analysis of policies that adapt stakeholders’ compensation or insurance to their risk exposure and that contribute to the long-term involvement of stakeholders. One can argue that corporate governance voice mechanisms ought to favor the representation of stakeholders according to their risk exposure level. Moreover, with this model we contribute to fulfilling the gap between an economic approach of the firm based on institutions and the expectations for sustainable development.