From the International Journal of Constitutional Law:
It is often asserted that the United States’ Constitution is the world’s most difficult to amend. But the basis for this empirical claim is shakier than one might imagine. This article introduces the small social science literature on measuring amendment difficulty and identifies several problems with it. We then go on to argue that a concept of an amendment culture is implicit in many discussions of amendment difficulty. We demonstrate empirically that the choice of amendment rule is a less important predictor of constitutional change than is amendment culture, measured as the rate of amendment in the immediately preceding constitution.