Almost 25 years ago, Scott Mainwaring and Timothy R. Scully published an edited volume, Building Democratic Institutions: Party Systems in Latin America (1995), that developed the concept of party system institutionalization and helped set the agenda for a wave of research on political parties in Latin America and beyond. Mainwaring’s latest edited volume, Party Systems in Latin America: Institutionalization, Decay, and Collapse, takes up where the previous work left off, surveying developments in Latin American party systems over the last few decades.

The new volume is much more than an update—it covers a great deal of new ground and makes a significant conceptual and empirical contribution to the literature on political parties. In the Introduction and the first two chapters, Mainwaring reconceptualizes party system institutionalization and uses the new concept to measure changes in it in the entire region since 1990. (Chapter 1 was coauthored with Fernando Bizzarro and Ana Petrova.) In Chapter 3, Mainwaring explores party system institutionalization’s consequences for democracy, and in Chapter 4, he and Bizzarro examine the factors that are correlated with party system institutionalization in the region. Chapters 5–11 consist of detailed case studies of party system stability and change in seven Latin American countries (Chile, Brazil, Mexico, Colombia, Argentina, Venezuela, and Peru), all of which were written by a distinguished group of U.S. and Latin American scholars. Chapters 12–15 consist of comparative analyses. Noam Lupu analyzes how the undermining of party brands contributed to partisan erosion and party breakdown in Argentina, Bolivia, and Chile in Chapter 12. Jason Seawright uses machine learning to examine party systems’ roots in society in Chapter 13, and Gustavo A. Flores-Macías explores the impact of party system institutionalization on economic policymaking and performance in Chapter 14. Finally, in Chapter 15, Allen Hicken and Rachel Beatty Riedl compare party systems in Latin America to those in Africa and Southeast Asia.

The most important contribution of the volume is the reconceptualization of party system institutionalization, which will, no doubt, be incorporated by future scholarship on this topic. In their 1995 volume, Mainwaring and Scully conceived party system institutionalization as having four dimensions: 1) the stability of interparty competition; 2) the strength of the parties’ roots in society; 3) the popular legitimacy of parties and elections; and 4) the solidity of party organizations. In this volume, however, Mainwaring and his collaborators (p. 17) dispense with the latter three dimensions on the grounds that they facilitate party system institutionalization but do not define it. The stability of interparty competition, they argue convincingly, represents the core of party system institutionalization. In highly institutionalized party systems, the main parties are stable, as are their vote shares, and their linkages to voters (p. 21). This reconceptualization focuses and simplifies the concept, and makes it easier to measure.

Another important contribution is with respect to measurement. In Chapter 3, Mainwaring identifies 13 indicators that can be used to measure party system institutionalization, and employs them to assess changes in party system institutionalization in all Latin American countries except Cuba. These indicators measure not only the stability in aggregate patterns of interparty competition but also the durability of the main contenders and the ideological stability of parties in the legislature. He uses these indicators to measure party system institutionalization in both presidential and legislative elections and with respect to different time periods. The measures yield similar trends and patterns of variance in most cases, and many of the results will come as no surprise to scholars of Latin American parties and elections. Although many scholars will not find it necessary to use all 13 indicators that Mainwaring has employed here, the indicators provide a useful range of measures that scholars can choose from to suit their own purposes. Moreover, Mainwaring has provided a great service by making this valuable data set available in an online appendix.

The third contribution is empirical. The volume significantly advances our understanding of the evolution of party systems in the region. Chapters 5–12 provide persuasive explanations for the consolidation, stasis, or decline of party system institutionalization in eight Latin American countries. They carefully show why and how party systems evolved during this period, and they discuss some of the consequences of these changes.

Nevertheless, Party Systems in Latin America is more of a conceptual and empirical contribution than a theoretical one. Many of the theoretical arguments in the volume have been made previously by the authors in other venues. For example, Chapters 3, 12 and 14 are all well done and largely convincing, but they draw extensively on arguments their authors have made in other books and articles. In addition, much of the volume is less concerned with developing general theories than it is with providing detailed descriptions of and explanations for the evolution of party systems in particular countries over time.

Causal inference is also an issue throughout the work, in part because it is very difficult to disentangle party system institutionalization from its purported causes and consequences. For example, it is hard to know whether greater party system institutionalization strengthens democracy or greater democracy strengthens party system institutionalization. Similarly, party system institutionalization may contribute to better economic performance, but better economic performance may also enhance party system institutionalization. In both of these instances, there are reasons to suspect reciprocal causation, as well as the existence of other unmeasured variables that shape party system institutionalization, democracy, and economic performance. Some of the chapters readily acknowledge these problems. In Chapter 4, which explores the correlates of party system institutionalization through quantitative analyses of 18 Latin American countries, the authors note the problem of endogeneity and caution that “the results are correlational, and limits to causal inference remain” (p. 130). Similarly, in Chapter 13, which examines the relationship between citizen attachments and party system institutionalization, Seawright warns that “the nature of the connection as causal, reverse-causal, spurious, etc., cannot be sorted out via the kind of descriptive analysis used here” (p. 396).

Finally, the volume might have benefited from a concluding chapter that summarized its findings, discussed their implications, and set out an agenda for future research. The final chapter, which compares party system institutionalization in Latin America to Africa and Southeast Asia, performs some of those tasks, but not as comprehensively as a concluding chapter might have done.

These shortcomings, however, do not negate the many strengths of Party Systems in Latin America. The volume represents an important empirical and conceptual contribution that will shape future research on party systems in Latin America and around the world.