Introduction: A Second Wave of Comparative Constitutional Studies

Most national constitutions last only a generation (Elkins, Ginsburg, and Melton 2009). As a result, at any time several countries are in the process of rewriting their highest-order law. For instance, at the time of this writing, constitution making is underway in Chile, Myanmar, and Tunisia. And even when constitutions are not being replaced, they are frequently amended (Versteeg and Zackin 2016; Dixon 2011). Constitutional change is thus a constant feature of most legal systems. The people in charge of constitution making confront several important decisions. One decision is whether to maintain parts of the old constitution or to start from a blank slate. Another decision is which substantive provisions to include. Should the constitution protect freedom of religion? Prohibit torture? Formally recognize gender equality? These questions were debated by drafters in 18th-century Philadelphia, 21st-century Katmandu, and hundreds of times in between. A related decision is whether to take a minimalist approach and constitutionalize only a limited set of particularly important values or to take a more maximalist approach to drafting. In addition to these substantive choices, constitution makers face the question of how public and participatory their drafting process should be. Finally, in the years after adoption, those governing under the new constitution must decide how to implement it and whether, and to what extent, to update it through interpretation or formal amendments. When confronted with these decisions, how do constitution makers know which choices would produce desirable outcomes? Unfortunately, there is relatively little empirical research available to help guide them. To illustrate, there is a long-standing debate, tracing back to Edmund Burke and Thomas Paine, on whether constitutional reform should be gradual or big-bang style, but there has not been much direct research on this question.1 There is also only a small amount of research addressing whether specific substantive provisions are associated with better outcomes (see Chilton and Versteeg 2015; 2020, pp. 59–78). Likewise, although there has been a lively normative debate over whether more might be less in constitutional design (compare Glendon [1991] with Greene [2021]), virtually no research addresses the question of whether including more topics will hurt a constitution’s overall performance. And while there is a growing consensus that inclusive and participatory constitution making is better for both democracy and the constitution’s prospects, the empirical evidence to support this claim remains somewhat limited (but see, for example, Eisenstadt, LeVan, and Maboudi 2017). Simply put, while they may have intuitions, scholars do not know much about what works in constitutional law. The reason is not that the consequences of these constitution-making choices are unimportant. Instead, the reason for the lack of knowledge is that getting empirical insight into these questions is hard, and perfect causal inference is rarely possible. In the past decade, however, a growing body of research has begun to tackle some questions relating to constitutional impact while taking causal inference seriously. To be sure, none of this research has solved the fundamental problems that make causal inference in constitutional law so difficult. These problems include the deeply endogenous relationship between the adoption of constitutional provisions and outcomes and difficulties with measuring constitutional laws and constitutional performance. But while this new wave of research has not solved these problems, it is making progress toward better understanding constitutions’ impact by embracing new approaches, collecting new data, and combining methods. We characterize this line of research as the second wave of research in comparative constitutional studies. This symposium grew out of the conference Measuring Impact in Constitutional Law, hosted by the University of Chicago on October 23, 2020, that was designed to help improve, promote, and highlight this new wave of research on constitutional impact.