The arbitrariness of supermajority rules

Abstract

There may be good general grounds for the adoption of supermajoritarian thresholds, but no such general arguments can justify the selection of a specific threshold. Although the benefits of supermajority rules, especially in the context of constitutional-amendment procedures, may outweigh the costs of their ex ante indeterminacy, the technically unjustifiable nature of specific thresholds means that those who are disadvantaged under such rules can be given no rational or reasonable explanation for their defeat other than the de facto power of coordination on a threshold. Political theory has a potential remedy in cases in which good reasons are not available, and in which bad reasons (such as the desire to ensure a veto for a powerful minority) might be brought to bear: randomization. If the benefits of supermajority rules are worth the costs of arbitrariness, we may wish to randomize the choice of threshold, though the move to do so may have its own negative consequences.