It is not very often that an edited book has the potential to carve a new niche in the field. This may be one of those rare volumes. The collection of essays edited by Gretchen Helmke and Steven Levitsky lays out a promising research agenda, not only for Latin Americanists but for students of democratization in general.

In the 1990s, the new institutionalism emerged as the dominant perspective for understanding the workings of democracy in Latin America. The analysis of electoral systems, parties, legislatures, presidential powers, and—more recently—judicial institutions yielded a vibrant intellectual production that had its most visible constituency in the Political Institutions Section of the Latin American Studies Association. At the same time, colleagues trained in the tradition of political sociology recurrently wondered: how could we assume that formal rules are the main explanatory variable in a region where the law is often ignored, distorted, or subverted by powerful political actors?

Informal Institutions and Democracy addresses this challenge by introducing a theoretical framework that bridges the study of formal and informal rules. The editors define informal institutions as “shared rules, usually unwritten, that are created, communicated, and enforced outside officially sanctioned channels” (p. 5). The unofficial, unwritten character of those norms determines their informality, but enforcement defines their “institutional” nature—in contrast to a vast array of other patterns of behavior that may have typified social meanings but are excluded from the definition. This element seems to distinguish Helmke and Levitsky's definition from the broader understanding of institutions advanced by the sociological school of symbolic interactionism (e.g., Peter Berger and Thomas Luckmann in The Social Construction of Reality, 1966).

The contributions to the volume dispel common misconceptions, for instance, that informal institutions are intrinsically detrimental to democracy, or that they only change very slowly. The introduction presents a typology based on whether existing formal institutions are strong or weak, and whether informal rules are consistent or inconsistent with the spirit of the law. The resulting four types (complementary, accommodating, substitutive, and competing informal institutions) provide a common framework that holds the book together. (Readers interested in a preview should check the piece published in Perspectives on Politics 2 [December 2004]: 725–40).

More challenging is the issue of how to identify informal institutions in empirical research. The editors offer valuable—but unfortunately brief—advice towards the end of the introduction (although the topic is also explored by Daniel Brinks in Chapter 10). Informal institutions can be documented through ethnographic research, or by predicting patterns of behavior consistent with hypothesized informal rules (including punishment for deviations) that can be established through comparative case studies or through the analysis of large-n samples.

Unfortunately, this brief review cannot do justice to the quality of the essays. The book is organized in four sections. The essays by Peter Siavelis (on power sharing in Chile), by Scott Desposato (on electoral markets and legislative behavior in two Brazilian states), and by Andrés Mejía Acosta (an insightful piece on ghost coalitions in Ecuador) reflect on executive–legislative relations. The essays by David Samuels (on campaign finance in Brazil), Michelle Taylor-Robinson (on clientelism and constituency service in Honduras), and Susan Stokes (on vertical accountability in four Argentine regions) depict the operation of informal institutions in the electoral arena. A set of chapters by Joy Langston (on the Mexican dedazo), John Carey and Siavelis (on electoral insurance in Chile), and Flavia Freidenberg and Levitsky (comparing informal party organization in Argentina and Ecuador) address the issue in relation to political parties. The fourth section features essays on informal institutions and the rule of law by Daniel Brinks (on the prosecution of police abuses in Argentina and Brazil), Todd Eisenstadt (on the use of informal agreements to solve electoral disputes in Mexico), and Donna Lee Van Cott (about community justice in the Andes). It is worth noting that the contributors are not mainstream dissidents but some of the best scholars among the institutionalist school of the last decade and a half. A brief but insightful essay by Guillermo O'Donnell (whose work in the mid-1990s ignited the debate on this subject) crowns the compilation.

This volume opens the road for a new political sociology, “a broad and pluralistic research agenda that encourages fertilization across disciplines” (p. 284). However, two challenges lie ahead. The first one is a better delimitation of the object of study. Central to the definition presented in the book is the idea that certain norms are “enforced outside officially sanctioned channels.” However, enforcement is broadly understood to include “hostile remarks, gossip, [and] ostracism” (p. 26), which makes the denotation of the concept of informal institutions quite broad. And the reference to nonofficial channels seems to recode one key word (informal) into another (unofficial), which leaves the connotation of the concept somewhat unresolved. (Stokes's suggestive distinction between game and grammatical rules in Chapter 6 further complicates the problem by extending the meaning of “rules”). A second challenge is the development of criteria to identify relevant instances of the phenomenon. Most institutional puzzles can be solved by invoking some “informal institution,” but this strategy would lead to a trivialization of the concept. Are informal institutions always to be evaluated with reference to a formal rule? It seems that every formal institution generates one or more related informal rules (an array of prescribed behaviors based on shared expectations about the interpretation of statutes, limits of enforcement, etc.), but not every informal rule has a formal counterpart. Thus, it is easy to find examples of weak formal institutions coexisting with strong informal ones, but I suspect that the opposite is not true (see pp. 274–81). In fact, this asymmetry may be critical for understanding issues of compliance and credible commitments because the development of “rational-legal” legitimacy at the formal level (to use Max Weber's terminology) may also require some degree of “traditional” legitimacy for complementary or accommodating informal norms.