The forthcoming article “The electoral politics of immigration and crime” by Jeyhun Alizade is summarized by the author below.

Immigration is one of the key issues shaping European politics in the last decades. A particular concern among voters is that it worsens crime problems. Despite the immigration-crime issue’s prominence in public debates and elite rhetoric, there have been comparatively few studies on its political consequences. Most of the literature on the electoral implications of immigration focuses on how (perceptions of) its cultural and economic consequences shape voting behavior and electoral outcomes.

Drawing on European Social Survey data, my article shows that fear of immigrant crime is less ideologically polarized than other immigration-related concerns. Unlike cultural or economic anxieties about immigration, which tend to divide voters along predictable partisan lines, safety-related concerns cut across party boundaries as well as educational and geographic divides, which usually polarize electorates on immigration.

The article introduces the idea of a voter-party mismatch: while Green and other progressive parties often avoid addressing crime among immigrants due to ideological and organizational constraints, many of their supporters express worries about immigrant crime. As a result, the mismatch can push progressive voters—particularly urban, educated ‘cosmopolitans’—toward center-right parties, which are more likely to problematize immigrant crime and push for law-and-order policies.

Empirical evidence from Germany supports this claim. In panel data and in a candidate-choice conjoint experiment, progressive voters concerned about immigrant crime are significantly more likely to switch their support to the center right, especially when the latter adopts stricter positions on issues like deportation of criminal foreigners relative to progressive parties. Notably, this shift does not appear to depend on whether the center-right simultaneously stigmatizes immigrants or adopts conservative socio-cultural positions—suggesting that basic safety threat can outweigh other ideological commitments among progressives.

Overall, my article shows that repercussions of immigration can in fact drive leftist cosmopolitans—usually perceived to be staunch supporters of immigration—to the right. As such, the article qualifies existing theories of electoral cleavages in contemporary knowledge economies, which posit a growing left-right divide on immigration due an educational re-alignment of voters.

About the author: Jeyhun Alizade is a postdoctoral research fellow in the Migration, Integration, Transnationalization research unit at the WZB Berlin Social Science Center. Their research “The electoral politics of immigration and crime” is now available in Early View and will appear in a forthcoming issue of the American Journal of Political Science.

The forthcoming article “Classification algorithms and social outcomes” by Elizabeth Maggie Penn and John W. Patty is summarized by the author(s) below.

Beyond Labels: How Algorithms Really Shape Our Lives (and Our Behavior) 

Algorithms, from credit scores to job applications, healthcare, and even how police decide where to patrol, influence everybody’s life. Some see these systems as neutral tools that simply categorize or “classify” things, like whether you’re creditworthy or a flight risk. In “Classification algorithms and social outcomes,” we present a theoretical analysis of what happens when algorithms don’t just classify people, but also change how people behave. 

For example, imagine a student preparing for a test. The test is designed to measure their college readiness, but if the student believes a high score will get them into a good college, they’ll likely “study for the test”. Similarly, if an algorithm is designed to detect fraud, people might commit less fraud, even if that wasn’t the algorithm’s direct stated goal. This is the core idea: people adjust their “life choices” based on how they expect an algorithm to classify and reward or punish them. 

This social scientific perspective on algorithmic design leads to some surprising and critical insights: 

• Accuracy Isn’t Always Neutral or Fair: One might assume an algorithm designed purely to be “perfectly accurate” would be “fair.” Our analysis shows that even with highly accurate data, an accuracy-maximizing algorithm can actually worsen inequality, pushing some groups towards desired behaviors (like obeying the law) and actively discouraging it in others.
• Algorithms Might Deliberately “Introduce Noise”: Counterintuitively, an algorithm designed to be accurate might — by design — make seemingly “inaccurate” decisions or reward people probabilistically.  Again, this “noise” isn’t a flaw; it’s a strategic choice by the algorithm to manipulate behavior more effectively.
• A More Punitive Designer Can Sometimes Be Better (for Individuals!): Another surprising finding is that increasing an algorithm’s payoff for punishing individuals (such as a ticketing algorithm) may actually make all individuals being classified better off in expectation. This happens because the algorithm, seeking to penalize more, might make non-compliance more appealing, a trade-off all individuals might prefer.

This research highlights that traditional ideas of “algorithmic fairness,” which often focus on statistical parity in classification errors, might be incomplete. When people’s behavior changes in response to an algorithm (a concept known as “performativity”), we need new ways to think about fairness. We offer one new way, which we call “aligned incentives,” which is satisfied by any algorithm that offers individuals in different groups similar behavioral incentives.  Finally, we believe our findings have implications for public policy, affecting areas like: 

• Housing and Lending: Algorithms influencing who gets housing or credit can shape financial decisions.
• Hiring: AI in hiring affects not just who gets jobs, but also who applies.
• College Admissions: Algorithms here can influence student preparation and application strategies.
• Tax Audits: The IRS’s algorithms, designed to detect under-reporting, also deter fraud, showcasing the tension between accuracy and behavioral goals.

Ultimately, we argue that, to truly understand the impact of algorithms, we must look beyond their technical definitions and consider the goals of those who design them and the resulting, sometimes unexpected, behavioral consequences for society. It’s a call to broaden our perspective on both how algorithms shape our world and how to evaluate the fairness of them. 

About the Author(s): Elizabeth Maggie Penn is a Professor of Political Science and Quantitative Theory and Methods at Emory University and John W. Patty is Professor of Political Science and Data & Decision Sciences at Emory University. Their research “Classification algorithms and social outcomes” is now available in Early View and will appear in a forthcoming issue of the American Journal of Political Science.

The forthcoming article “The nation-state, non-Western empires, and the politics of cultural difference” by Loubna El Amine is summarized by the author below.

In much contemporary political theory, the concept of empire is almost always equated with Western imperialism and colonialism, where non-Western societies were subjected to European domination. But this focus overlooks the fact that, for much of recorded history, vast regions of the world were governed by non-Western precolonial empires. The legacies of these empires continue to shape present-day politics and remain subjects of debate among postcolonial thinkers.

My focus in this article is on these empires’ government of cultural diversity. Examining three cases, the Mughal Empire, the Qing Empire, and the Ottoman Empire, I argue that these empires achieved what I describe as incorporation — a mode of rule that integrated multiple communities without requiring their homogenization. The contrast here is with the modern nation-state, which operates within a rigid majority–minority framework.

I elicit three institutional features that allowed empires to achieve such incorporation. First, their governing structures were plural: a multiplicity of entities with political authority intertwined with a multiplicity of religious, ethnic, and linguistic communities with their own governing structures. Second, relations between the center and the periphery were heterogeneous: different regions and communities were governed according to different legal codes, practices, and degrees of autonomy. The center did not speak in one voice. Third, their authority was non-territorial in a modern sense: boundaries were fluid, overlapping, and not defined by the strict citizen–foreigner divide characteristic of nation-states.

These arrangements made possible ambitious normative ideals of inclusive peace. The Mughals articulated sulh-i kull (“peace toward all”), the Qing invoked the concept of tianxia (“all under Heaven”), and the Ottomans pursued nizam-i alem (“world order”). While these ideals were never fully realized, they were nonetheless made plausible by the imperial framework in a way that they no longer are within the institutional logic of the modern state.

While my aim is not to argue that we should somehow resurrect empires simply because they accommodate cultural difference well, the exploration of non-Western precolonial empires, as historical examples that have not yet been studied by political theorists, aims to contribute, if only indirectly, to the production of new global imaginaries. It is meant to complement what can be broadly identified as cosmopolitan proposals envisioning forms of government beyond the nation-state and, more specifically, to contribute to recent efforts to recover historical alternatives to the state model, primarily federal and other similar arrangements.

About the Author: Loubna El Amine is a Lecturer in the Department of Political Economy at King’s College London. Their research “The nation-state, non-Western empires, and the politics of cultural difference” is now available in Early View and will appear in a forthcoming issue of the American Journal of Political Science.

The forthcoming article “Change in migrants’ political attitudes: Acculturation and cosmopolitanization” by Eva Krejcova, Filip Kostelka, and Nicolas Sauger is summarized by the author(s) below.

How does migration shape individuals’ political attitudes? Do migrants retain attitudes acquired in their countries of origin, or adopt those of their new societies? With nearly one in five residents in developed democracies born abroad, the answers carry major implications for democratic politics. Yet, existing evidence remains fragmented and often contradictory. We provide a new theoretical framework, innovative methods, and rich empirical findings that help untangle the complexity of migrants’ political resocialization and reconcile divergent conclusions in earlier studies.

Researchers have long debated whether migrants resist change or acculturate into their host societies. We formalize this debate by constructing a one-dimensional, Euclidean space. The attitudinal distance between sending and receiving countries constitutes a continuum. At one end lies full attitudinal alignment with the country of origin (resistance); at the other, complete adoption of host-country attitudes (acculturation).

Previous studies implicitly assumed that migrants’ attitudes are positioned between those of locals in sending and receiving countries. We argue that certain attitudes may lie beyond this continuum, as they are likely transformed by the migration experience itself. We call them transnational attitudes, distinguishing them from polity-specific attitudes, rooted in national contexts. We hypothesize that migration triggers cosmopolitanization of transnational attitudes and acculturation of polity-specific attitudes: migrants become distinctively supportive on transnational issues, while increasingly resembling locals in their new country on polity-specific issues.

We test our hypotheses using cross-sectional and panel data spanning nearly 380,000 observations from 104 sending and 28 destination countries. We apply our typology to four dimensions of political competition in contemporary Europe: redistribution, homosexuality, European integration, and immigration. Migrants’ embedding in two national contexts—origin and destination—poses challenges for statistical modelling. To address them, we combine the estimated dependent variable method with the logic of counterfactuals. This new approach, applicable to a range of other research problems, allows us to compare migrants with counterfactual locals in both sending and receiving countries.

Our analysis proceeds in three steps. First, we compare migrants’ and locals’ positions on each of the four issues. Next, we use panel data to examine the evolution of migrants’ attitudes over time. Finally, we pioneer an empirical inquiry into self-selection. Leveraging survey data on migration intentions and panel metadata, we assess whether potential differences between migrants and locals precede migration.

Our results reveal the remarkable malleability of migrants’ attitudes. On polity-specific issues—such as redistribution and homosexuality—migrants’ tend to acculturate to the host country over time. But on transnational issues—immigration and European integration—they hold consistently more supportive views than locals. These patterns are not explained by self-selection: potential and future migrants attitudinally resemble stayers before migrating.

Besides the new theoretical and methodological tools, our readers may take away three main empirical insights. First, while migrants’ polity-specific attitudes acculturate, their transnational attitudes do not—bringing more supportive views on immigration and European integration into their host societies. Second, migrants’ attitudinal change provides strong evidence of adult political resocialization. Finally, individuals sometimes combine culturally conservative and cosmopolitan views—reflecting different logics of attitudinal change. Our theory and findings help explain these hybrid attitudinal configurations in contemporary democracies.

About the Author(s): Eva Krejcova is a Junior Lecturer at IDHEAP, University of Lausanne, Filip Kostelka is a Professor of Political Science, Chair in Political and Social Change, and Director of Graduate Studies in the Department of Political and Social Sciences (SPS) at the European University Institute (EUI), and Nicolas Sauger is a University Professor at Sciences Po Paris. Their research “Change in migrants’ political attitudes: Acculturation and cosmopolitanization” is now available in Early View and will appear in a forthcoming issue of the American Journal of Political Science.

The forthcoming article “Competitive diplomacy in bargaining and war” by Joseph J. Ruggiero is summarized by the author below.

Diplomacy can advance state interests; however, if each side of a zero-sum dispute can use diplomacy to improve its terms of peace, these efforts are fundamentally competitive. This paper introduces the concept of competitive diplomacy to crisis bargaining, which is defined by three core properties: (1) it is costly, (2) it does not enhance a country’s war payoffs, and (3) it can improve a country’s payoff from cooperation. Competitive diplomacy as such becomes a channel through which characteristics of a potential war can affect the quality of peace, makes cooperation less efficient, and affects a country’s propensity to fight. How does the incentive to compete in diplomacy affect the prospects of cooperation?  Which settings fare well at averting conflict while simultaneously preserving the largest gains from peace?

To answer these questions, I develop a game-theoretic model of war that captures the core trade-off between internalizing the gains from cooperation and exerting costly effort to reach preferable peace deals. There are two key ingredients of the model that establish novel results. First, while existing models treat proposers as either predetermined or randomly recognized by exogenous probability, my approach treats agenda-setting power as endogenous to a country’s performance in pre-bargaining competition. Second, this paper allows periodic outcomes to persist into the future at varying rates, which affects a country’s incentive to cooperate and their willingness to compete.

The analysis reveals new insights. First, I find that costly wars endogenously create costly peace. Even if wars never occur on the path of play, greater costs of war imply a larger surplus from cooperation. As the surplus expands, agenda-setting power becomes more valuable, creating a stronger incentive to engage in competitive diplomacy. The model also identifies when war is more efficient than cooperation. After a division of the pie is reached, through war or cooperation, it persists until an opportunity to renegotiate arises. Countries are then driven to fight efficient wars by two forces: the (exogenous) differential persistence of outcomes and the (endogenous) equilibrium effort in competitive diplomacy. The logic is analogous to that of “ripping off the bandage.”

I then extend the model to examine how frictions to cooperation affect the incentives for diplomatic competition and conflict, finding that states may risk delay in attempt to free ride on their adversary’s efforts in obtaining peace. As a result, frictions simultaneously protect against the erosion of the bargaining surplus caused by competitive diplomacy. Likewise, the model suggests that the Pareto optimal level of competition counterintuitively maximizes the probability of delay when peace deals are reliable. Reliable peace deals that avert efficient wars therefore create a trade-off between welfare and timely settlement.

The model predicts that there will not be an association between competitive diplomatic efforts and cooperative gains in equilibrium across cases. The analysis also highlights that changes to the international environment, as opposed to specific characteristics of a bilateral relationship, can give rise to war. Further, the extension to consider settlement frictions has implications on how peace mediators should approach conflict resolution in contemporary crisis situations: the model suggests that reducing frictions to cooperation—while reducing delay—can actually make both sides worse off.

About the Author: Joseph J. Ruggiero is an assistant professor in the Department of Politics at the University of Virginia. Their research “Competitive diplomacy in bargaining and war” is now available in Early View and will appear in a forthcoming issue of the American Journal of Political Science.

The forthcoming article “Balancing bossism: State expansion in the face of elite capture” by Anna F. Callis and Christopher L. Carter is summarized by the author(s) below.

Central governments often rely on local elites to implement policies in distant regions. While this can extend state influence, it can also lead to a single elite (a political boss) dominating local politics and obstructing state initiatives. Our research examines how weak states can counter this challenge through balancing—creating new local positions with distinct appointment rules that offset the power of local bosses. We analyze turn-of-the-20th-century Peru, where local bosses often captured justices of the peace, key positions of local authority, to create and reinforce their monopoly on local power. We leverage a natural experiment in population-based appointment rules to show that—in areas with a justice of the peace—the Peruvian government introduced lieutenant governors, who operated under different appointment criteria and were thus autonomous from local bosses. We show that this balancing strategy allowed the central state to implement policies that bosses frequently opposed, including an important education census.

The implications of elite capture for state capacity extend far beyond historical Latin America. In peripheral areas across the Global South today, figures such as mining companies, warlords, drug gangs, and political brokers exert considerable control, often shaping state capacity to serve their interests. Our findings suggest that instead of directly confronting powerful elites—an option that may be infeasible for weak states—governments can strategically reconfigure local authority to foster competition among elites. This approach presents a potentially viable strategy for policymakers seeking to implement reforms in regions where entrenched interests have long resisted state intervention.

About the Author(s): Anna F. Callis is an Assistant Professor in the Department of Government and Law at Lafayette College and Christopher L. Carter is an Assistant Professor in the Department of Politics and John L. Nau III Assistant Professor of the History and Principles of Democracy at the University of Virginia. Their research “Balancing bossism: State expansion in the face of elite capture” is now available in Early View and will appear in a forthcoming issue of the American Journal of Political Science.

The forthcoming article “States, cities, and border control: Do sub-state collectives have a right to protect vulnerable people on the move?” by Kim Angell is summarized by the author below.

“A standard argument in favor of a state’s right to control its borders appeals to the value of collective self-determination. The idea, roughly, is that a state’s members have a morally significant interest in freely determining the values, goals, and practices that apply within their territory. Outsiders may bring unwanted changes, either by taxing the state’s resources or by introducing different values, goals, and practices. Collective self-determination, therefore, typically requires rights of border control. However, the state’s right to control its borders is not absolute. Outsiders have a significant interest in the protection of basic human rights, and each state must do its share in extending such protection to vulnerable people on the move. But as long as the state has fulfilled its ‘fair share’ (whatever that may be), it may exercise discretionary border control beyond that. Or so the standard argument from self-determination goes.

This paper challenges the self-determination argument on its own terms. The key idea is that what is valuable for state collectives might also be valuable for substate collectives. If we are to consistently value collective self-determination, we must look beyond the state level and consider whether substate collectives—such as cities—may also have relevant interests in immigration policy.

In many cases, cities have expressed strong solidarity with vulnerable people on the move, declaring their willingness to protect additional vulnerable immigrants—above and beyond those protected by the state. The paper discusses various examples of this, both from Europe (e.g., the Solidarity Cities network) and North America (e.g., the sanctuary city movement). If cities have such relevant goals and are capable of self-determination, they have a valid claim to protect additional vulnerable people on the move. This holds regardless of whether those people are UN Convention refugees, asylum seekers, unauthorized immigrants, or individuals with various liminal legal statuses.

A city’s claim to protect additional vulnerable people on the move must, of course, be balanced against the state’s claim to close its borders. After all, if self-determination matters, it must matter on both sides. Yet, as the paper demonstrates, this balancing process will inevitably result in a moral right for the city to protect an additional quota of vulnerable people on the move. While the exact size of this quota will vary from case to case, it will never be empty.

This result is quite surprising, given that the value of self-determination has traditionally been used to defend strong rights of border control for states. A key message of this paper, then, is that one of the most central arguments in the debate on immigration and border control must be reassessed.”

About the Author: Kim Angell is a Research Programme Manager at The Norwegian Nobel Institute. Their research “States, cities, and border control: Do sub-state collectives have a right to protect vulnerable people on the move?” is now available in Early View and will appear in a forthcoming issue of the American Journal of Political Science.

The forthcoming article “Unpacking the role of in-group bias in US public opinion on human rights violations” by Rebecca Cordell is summarized by the author below.

Americans are more likely to oppose human rights abuses perpetrated by a political out-group. Simply changing the perpetrator’s political party—from an in-group to an out-group—can determine whether individuals oppose their government’s human rights violations.

To understand what shapes public responses to domestic human rights violations, I conducted a national conjoint survey experiment with 3,200 US respondents. Participants evaluated different physical integrity rights abuse scenarios (including arbitrary arrests, torture, extrajudicial killings, and enforced disappearances) according to their disapproval and willingness to mobilize against the abuse.

For each violation, I varied the perpetrator and elite cue giver’s party affiliation and the target’s race, religion, and citizenship, as well as other contextual factors. To identify the effect of in-group bias, I compared how respondents reacted to abuses when they shared identities with these actors versus when they did not. Examining the relative influence of different identity characteristics is important, as an individual (bystander observing the violation) may have multiple connections to the actors in abuses at the same time.

Results show the perpetrator’s identity plays a key role in shaping respondents’ choices. Individuals are more likely to oppose abuses when the perpetrator is from the opposing political party. These patterns held across different political leaders, from US governors to presidents, and applied to both Democrat and Republican supporters. However, there are limits to partisan loyalty. In-group perpetrators are less likely to get away with targeting their supporters’ racial in-group or when bystanders share many identities with targets and elite cue givers.

Why does the perpetrator’s party identity matter so much? In U.S. politics, party loyalty dominates public attitudes on a range of topics, and people tend to see political leaders as the ones responsible for protecting rights. This hierarchy of blame can trigger strong in-group defenses to protect the group’s moral reputation, and punitive out-group demands for accountability. This powerful focus on the perpetrator can overshadow concern for the victim and make it harder for political elites to shift public opinion on abuses.

These findings have serious implications for policymakers and human rights groups. In democracies, human rights depend on public accountability, and public opinion can play a crucial role in shaping government behavior. While Americans are more likely to oppose abuses by political opponents, they may be inclined to excuse or overlook violations committed by their own side. This can reduce the political costs of repression and make it easier for governments to evade accountability.

About the Author: Rebecca Cordell is an Assistant Professor in the Department of Political Science at the University of Pittsburgh. Their research “Unpacking the role of in-group bias in US public opinion on human rights violations” is now available in Early View and will appear in a forthcoming issue of the American Journal of Political Science.

The forthcoming article “The logic of secret alliances” by Peter Bils and Bradley C. Smith is summarized by the author(s) below.

A primary goal of military alliances is to deter aggression from enemies. Traditionally, alliances are understood to achieve this goal by serving as a costly signal of members’ commitment to fight alongside one another against a shared enemy. By observing allies engage in costly action such as policy coordination or the provision of military equipment, enemies infer that only states seriously committed to each other’s defense would bear these costs. Through this logic, alliances alter the calculus of deterrence and reduce an enemy’s incentive to attack.

In light of this signaling logic, secret alliances stand out as odd. For the signaling mechanism to operate, it is self-evident that an alliance, and the costs imposed by it, must be visible to adversaries. This presents a puzzle: if a primary goal of alliances is to deter enemies through signaling, then why would allies keep their commitments to one another secret?

In this paper, we argue that secret alliances are an attractive option when the alliance may act as a signal of members’ alignment. In our theory, alliances play two roles. First, they aggregate capabilities, allowing members to better resist aggression from a shared enemy. Second, and importantly for our argument, the presence of an alliance may endogenously reveal information about the constellation of interests in the international system. Consequently, a new alliance can indicate that a state previously thought to be friendly is, in reality, an adversary. We argue that if there is significant uncertainty about the alignment of states’ interests then the second effect dominates and secret alliances emerge.

To develop this argument, we analyze a formal model in which states may enter into secret or public alliance agreements. We find that if there is uncertainty about the alignment of interests then secret alliances occur in equilibrium. We also find that secret alliances have general effects on deterrence, undermining the deterrent value of concurrent public alliances.

Our theory explains variation in the prevalence of secret alliances over time. Prior to World War I secret alliances were the norm. However, by the Cold War era they are virtually non-existent.  Our model points to the emergence of two phenomena after World War II to explain this pattern. First, the movement of the international system from a multipolar to bipolar environment reduced uncertainty about states’ alignments. Second, the advent of nuclear weapons significantly increased the deterrent value of alliances, further mitigating the need for states to maintain secrecy about their alignments.

About the Author(s): Peter Bils is an Assistant Professor of Political Science and Economics at Vanderbilt University and Bradley C. Smith is an Assistant Professor in the Department of Political Science at Vanderbilt University. Their research “The logic of secret alliances” is now available in Early View and will appear in a forthcoming issue of the American Journal of Political Science.

The forthcoming article “Complementarity in alliances: How strategic compatibility and hierarchy promote efficient cooperation in international security” by J. Andrés Gannon is summarized by the author below.

How can defense alliances effectively harness the benefits of collective action when faced with significant coordination challenges and the risks of opportunism? This study investigates the conditions under which states can overcome these inherent difficulties to achieve efficient cooperation in international security. I argue that alliances characterized by high strategic compatibility and a hierarchical structure are better equipped to minimize opportunism and coordination costs. This, in turn, facilitates an efficient distribution of defense capabilities among member states, fostering complementarity and a functional division of labor rather than promoting redundant military investments.

To assess this theoretical framework, I develop a novel network-level measure of the division of labor within alliances. This measure is applied to an extensive dataset of national military capabilities spanning from 1970 to 2014. The empirical analysis also incorporates improved measures of strategic compatibility—defined as the extent to which states concur on the nature of the international threat environment—and hierarchy, understood as an asymmetric distribution of influence over security decisions within the alliance.

The findings indicate a robust positive association: alliances with high strategic compatibility and greater hierarchy exhibit a significantly higher division of labor. This suggests that shared security interests and centralized decision-making structures within an alliance are crucial factors that mitigate the inherent costs of collective action, enabling a more rational and efficient allocation of defense responsibilities.

This research offers several contributions to the understanding of international security. It clarifies the interaction between alliance structures and armament policies, demonstrating that the distribution of military capabilities within an alliance is shaped by the alignment of security interests and the nature of its decision-making framework. Furthermore, it introduces complementarity as a distinct mechanism through which alliances can enhance the efficiency of defense spending and collective security outcomes. Finally, the study challenges the conventional view of states as undifferentiated “like-units” in the international system by providing evidence of functional differentiation emerging from cooperative security arrangements. These insights underscore the importance of alliance design in promoting efficient and effective international security cooperation.

About the Author: J. Andrés Gannon is an Assistant Professor of Political Science at Vanderbilt University and a Faculty Affiliate at the Data Science Institute. Their research “Complementarity in alliances: How strategic compatibility and hierarchy promote efficient cooperation in international security” is now available in Early View and will appear in a forthcoming issue of the American Journal of Political Science.