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 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.