It has become almost universal practice for countries to adopt formal constitutions. Little is known empirically, however, about the evolution of this practice on a global scale. Are constitutions unique and defining statements of national aspiration and identity? Or are they standardized documents that vary only at the margins, in predictable and patterned ways? Are constitutions becoming increasingly similar or dissimilar to one another over time, or is there no discernible overall pattern to their development? Until very recently, scholars have lacked even basic empirical data on the content of the world’s constitutions, much less an understanding of whether there are global patterns to that content.

This Article offers the first empirical account of the global evolution of rights constitutionalism. Our analysis of an original data set that spans the rights-related content of all national constitutions over the last six decades confirms the existence of several global constitutional trends. These include the phenomenon of rights creep, wherein constitutions tend to contain an increasing number of rights over time, and the growth of generic rights constitutionalism, wherein an increasing proportion of the world’s constitutions shares an increasing number of rights in common.

Perhaps our most striking discovery is that 90% of all variation in the rights-related content of the world’s constitutions can be explained as a function of just two variables. Both of these variables are underlying traits of a constitution that can be measured quantitatively. The first variable is the comprehensiveness of a constitution, which refers simply to the tendency of a constitution to contain a greater or lesser number of rights provisions. The second variable is the ideological character of the constitution. We find empirically that the world’s constitutions can be arrayed along a single ideological dimension. At one end of the spectrum, some constitutions can be characterized as relatively libertarian, in the sense that they epitomize a common law constitutional tradition of negative liberty and, more specifically, judicial protection from detention or bodily harm at the hands of the state. At the other end of the spectrum, by contrast, some constitutions are more statist in character: they both presuppose and enshrine a far-reaching role for the state in a variety of domains by imbuing the state with a broad range of both powers and responsibilities. For every constitution in the world, we calculate a numerical score that measures its position on this ideological spectrum. These scores yield an ideological ranking of the world’s constitutions – the first of its kind.

Using these scores, we are able to map the ideological evolution of global constitutionalism. We show that the world’s constitutions are increasingly dividing themselves into two distinct families – one libertarian in character, the other statist. Within each family, constitutions are becoming increasingly similar to one another, but the families themselves are becoming increasingly distinct from one another. The dynamics of constitutional evolution, in other words, involve a combination of ideological convergence and ideological polarization.

David S. Law & Mila Versteeg, The Evolution and Ideology of Global Constitutionalism, 99 California Law Review, 1163–1257 (2011).