The informational role of supermajorities

We study a collective decision making environment where an agenda setter makes strategic proposals to privately informed voters who vote strategically. We show that, consistent with empirical evidence, it can be optimal for the agenda setter to propose supermajorities. Due to an informational role that we unveil, optimal supermajorities can be less costly than minimum winning coalitions, even though more voters are awarded a positive share. We also examine consequences in terms of quality of decision making. We show that the introduction of a strategic agenda setter can lead to socially suboptimal decisions. (C) 2008 Elsevier B.V. All rights reserved.