Does the Constitutional Amendment Rule Matter at All? Amendment Cultures and the Challenges of Measuring Amendment Difficulty

Abstract

It is often asserted that the United States’ Constitution is the world’s most difficult to amend. But how do we really know this? This paper unpacks the tricky methodological issues in measuring flexibility cross-nationally. We find that the various metrics of amendment difficulty offered in the literature are poorly correlated, suggesting potential validity problems. This illustrates a general challenge of institutional accounts of constitutional behavior. Institutions surely matter, but institutional explanations are, like all explanations, always partial. For some matters, behavior may be more driven by political or social factors that can overcome the powerful force of institutional incentives. We argue that amendment difficulty is an example of just such a matter, and provide an alternative theory of amendment difficulty, the key element of which is amendment culture. Drawing on new data, we develop a simple indicator of amendment culture and show empirically that this does a better job of explaining observed patterns of amendment within constitutional systems than do any of the institutional indices or variables on offer. Our article thus offers both a critique of the existing literature and a way toward understanding why constitutional systems vary in their rates of amendment.