The defining feature of democracy may be electoral competition, but elected lawmakers, especially women, spend large amounts of time cooperating. Explaining when and why this collaboration occurs forms the core of Tiffany D. Barnes’s Gendering Legislative Behavior. Barnes argues that collaboration depends on incentives and constraints: Legislators cooperate in order to overcome their structural marginalization and attain policy power, but electoral institutions, party seat share, individual characteristics, and policy priorities will shape their ability and willingness to do so. This detailed analysis, which draws primarily on cosponsorship data from 23 provincial legislative chambers in Argentina between 1992 and 2009, demonstrates that female lawmakers’ bill coauthorship differs systematically from that of male lawmakers. Sidelined in terms of their access to chamber and committee leadership posts, women collaborate more than men, especially when party control over their careers is low. By attending carefully to the gendered nature of incentives and constraints, Barnes’s work critically and crucially challenges gender-blind accounts of legislative behavior: Scholars should not assume that male and female lawmakers respond similarly when faced with comparable decision environments.

Prior research on gender and legislative behavior has shown that female legislators rarely hold the highest-ranked or most-prestigious positions within the chamber or the party delegation; that they display more inclusive and cooperative work ethics; that they author, cosign, and advocate for legislation benefiting women, children, and families; and that the successful implementation of gender quota laws raises women’s presence in the chamber. Barnes draws these four insights together. She begins by arguing that female legislators’ institutional marginalization, combined with gender role socialization that rewards inclusive behavior, increases their incentives to collaborate relative to male lawmakers. Even so, collaboration entails a cost–benefit calculation, one mediated by institutional, partisan, and contextual factors that create variation both between and within chambers. Different electoral institutions vary party control and women’s total numerical representation between chambers; women’s seniority, their membership in the governor’s party, and whether the legislation addresses women, children, and family shape the individual benefits of collaborating within chambers. In examining how each variable raises or lowers female legislators’ incentives to collaborate, Barnes uses rational choice analysis to unpack gender differences in legislators’ behavior.

In general, Barnes finds that women collaborate more than men, primarily with other women, both within their own parties and across party lines. Female legislators collaborate at higher rates when their numbers in the chamber are few. These patterns then diverge as women’s numerical representation increases, with women elected from districts that give party leaders high control over their futures cooperating less, and women elected from districts that give party leaders less control over their futures cooperating more. In other words, women’s collaboration does not challenge party leaders’ agenda or programmatic control when their numbers are few, but as women cross the 20% threshold, their collaboration becomes more threatening. Women with greater freedom can more successfully withstand party leaders’ displeasure, and will continue to collaborate at high rates, while their female colleagues with less freedom will reduce their cooperative efforts. This pattern repeats itself even when the sample is divided between senior and junior legislators, and between legislators of the governing party and the opposition. However, the pattern disappears for the subset of legislation benefiting women, children, and families. Women collaborate with copartisans and across party lines to advance gender-friendly legislation, no matter the degree of party control.

Barnes’s principal contribution thus hinges on her conceptualization and operationalization of party constraints, which differs from both party ideology and party discipline. Left–right preferences exert little influence over lawmakers’ collaborative behavior, because Argentina’s political parties are often nonideological, and because Barnes considers all cosponsored legislation, irrespective of substantive goals. Whereas scholars typically measure party discipline by looking at whether the electoral system as a whole encourages personal vote seeking or party loyalty, Barnes drills down to the district level. She argues that legislators elected from large districts depend on the party, because leaders determine ballot ordering, whereas legislators elected from small or medium districts (whether single or multimember) can behave more entrepreneurially.

The data support Barnes’s intuition that district size, which creates within-system variation, shapes cosponsorship behavior, but her causal story depends significantly on party leaders’ omniscience. Do party leaders really use district size as a heuristic when determining whose behavior to police? Do party leaders really know about and react to every initiative coauthored by their rank and file? Party leaders may only monitor and squash initiatives that diverge from their central objectives, and may only react if such legislation appears likely to pass through committee. Women’s structural marginalization, which Barnes shows to persist even as their numerical representation rises, suggests a general devaluing of women’s legislative contributions—which should further fuel party leaders’ neglect. District size may not motivate party leaders’ scrutiny, but may generate selection effects: Perhaps legislators who successfully run in smaller districts are already more assertive, confident, independent, and skilled. Barnes’s work invites scholars to further unpack the causal mechanisms underlying district size, especially as it interacts with female politicians’ character and careers.

In addition to the quantitative models, the book displays Barnes’s impressive case knowledge and meticulous attention to detail. She uses her qualitative data particularly well, deploying quotes from Argentine lawmakers to both develop her theoretical expectations and reinforce her statistical results. For instance, her interviews reveal that female lawmakers use cosponsorship as more than a signaling device: for marginalized legislators, cosponsorship allows them to shape policy content and build the alliances necessary to win policy change.

Barnes further develops this story in her comparative chapter. Case studies from the national legislatures of Rwanda, South Africa, the United States, and Uruguay offer variation on party constraints (low in Rwanda and the United States and high in South Africa and Uruguay), as well as women’s numeric representation (only above 30% in Rwanda). Here, she operationalizes collaboration as women’s formal or informal caucusing. This important look at other modes of cooperative behavior raises further questions about the relationship between policy advocacy and party constraints. For example, Uruguayan women’s low numbers allow their activities to “fly under the radar” (p. 198), but the women’s caucus receives significant civil society support and media attention—which surely attracts party leaders’ attention. Women’s caucuses may insulate female legislators from party leaders’ retaliation, and even generate the public pressure necessary to persuade party leaders to accept their proposals. Notably, successful collaborations entailed legislating against gender-based violence in Rwanda and passing gender quotas in Uruguay: While not uncontroversial, neither measure substantially challenges entrenched religious or doctrinal beliefs. As Barnes intimates—but does not directly state—caucuses may both facilitate collaboration and overcome party constraints when the proposed status quo shift is small. Future work should examine the kind of legislation on which women collaborate, asking whether party constraints vary depending on whether the legislation’s substantive goals challenge vested interests.

In summary, Barnes persuasively demonstrates that democracy entails significant cooperation, that female legislators collaborate to overcome their structural marginalization, and that institutional, partisan, and contextual variables mediate these trends. Her well-reasoned and well-argued analysis demonstrates why comparative politics scholars must take gender seriously: Across the globe, women’s legislative representation is increasing, and models of lawmaking behavior that do not account for gender differences in legislators’ cost–benefit calculations will underexplain policy outcomes. As such, Gendering Legislative Behavior constitutes required reading for comparative politics scholars.