The Paradox of New Members: Strategic Foundations and Experimental Evidence

Power indices suggest that adding new members to a voting body may affect the balance of power between the original members even if their number of votes and the decision rule remain constant. Some of the original members may actually gain, a phenomenon known as the paradox of new members. We show that the paradox can occur as an equilibrium of a noncooperative bargaining game based on the Baron-Ferejohn (1989) model of legislative bargaining. We implement this game in the laboratory and find empirical support for the paradox.