Research

My research focuses on the drivers of international and civil conflict, the causes and consequences of nuclear proliferation, and the effect of institutions on international security.

My research focuses on the drivers of international and civil conflict, the causes and consequences of nuclear proliferation, and the effect of institutions on international security. Much of my work examines the role of uncertainty in international relations, and the mechanisms by which parties seek to resolve this uncertainty.
 

Book Project

The Constraining Power of the Nuclear Nonproliferation Regime

Portions presented at the ISA Annual Conference (2014, 2016), PEIO Conference (2014, 2016), APSA Annual Meeting (2013–2015), Nuclear Studies Research Initiative (2015), TISS New Faces Conference (2014), and the MPSA Annual Meeting (2013).

This project examines how the nuclear nonproliferation regime, and international security institutions more generally, affect the behavior of states. These institutions seem to defy existing theory: punishment is difficult and information hard to come by, yet security institutions often boast near-universal membership and seem to enjoy high levels of compliance. I argue that these institutions can effectively constrain state behavior because states use the accession and compliance decisions of others as important clues about the efficacy of an institution and about the underlying policy preferences of members and non-members alike. I test my hypotheses using data on states’ pursuit of nuclear weapons and their membership in the various international agreements that make up the nuclear nonproliferation regime. I not only identify strong support for the constraining power of the nuclear nonproliferation regime, but also find that the decision of a state to seek nuclear weapons is conditioned to a surprising degree on the compliance of the overall population of member states. At the same time, how the international community responds to a state’s nuclear weapons pursuit depends heavily on the extent to which it is embedded within the larger regime complex.



  • Chapter 1: State compliance and the track record of the nuclear nonproliferation regime

  • ► Abstract


By most theories of international relations, the nuclear nonproliferation regime ought to be a failure: the regime imposes substantial obligations and costs on its membership, punishment of non-compliance is difficult, and information is hard to come by. Yet the nonproliferation regime boasts near-universal membership and seems to enjoy high levels of compliance. Why, then, does the nuclear non-proliferation work? This chapter proposes a new theory of compliance in which a state’s decision to abide by an international commitment is driven by the track record of the institution. Security institutions like the nonproliferation regime are based on a fundamental bargain among member states: each member is willing to comply only so long as others do. There is often significant uncertainty, however, surrounding the compliance behavior of others and the effectiveness of the institution in constraining state behavior. The track record of the institution provides information that helps to resolve this uncertainty. As time passes with few violations, states will in turn be more likely to comply themselves; evidence of rampant noncompliance, on the other hand, will make states more likely to cheat. Analysis of data on nuclear weapons programs between 1968 and 2010 finds that members of the nuclear nonproliferation regime are more likely to pursue nuclear weapons when there have been a greater number of recent violations of the regime. The chapter’s findings have important implications for nonproliferation policy, where long-term, multilateral efforts to bolster the credibility of the nuclear nonproliferation regime have often taken a back seat to short-term, bilateral foreign policy goals.




  • Chapter 2: Breadth versus depth in international security institutions

  • ► Abstract
  • |
  • Paper

Several international security institutions appear both broad and deep—they impose significant obligations on state parties but still enjoy a large membership. This chapter examines this empirical puzzle, theorizing that in some cases—when it is costly both to abstain from and to be found in violation of an agreement—there is no broader versus deeper tradeoff. High obligation may actually be necessary for large membership, because states will only join institutions when they expect other member states to comply. I find that states are more likely to join the nuclear nonproliferation regime when there is a strong track record of compliance with the institution, lending support to this theory. The results in this chapter are important both for theories of institutional design and for policy discussions surrounding the risks of state withdrawal from elements of the nuclear nonproliferation regime.



International security institutions often lack formal enforcement mechanisms, but this does not mean that violations of international commitments always go unpunished. States that violate treaties routinely face pressure from others to change their behavior, including through sanctions and military attack. But the lack of formal enforcement measures probably does contribute to significant variation in which states are targeted for punishment—enforcement is nearly always at the discretion of the punishing state. Why do some states face punishment while the transgressions of others are overlooked? I argue that enforcing states look to the policy preferences of violators for signals about the likelihood that enforcement will change state behavior and the cost to the international community of allowing the violation to continue. Patterns of institutional membership within a larger regime help to credibly reveal the preferences of state parties. I use data on membership in the various agreements that make up the nuclear nonproliferation regime to derive a new measure of state preferences over nonproliferation policy issues, applying an item-response theory model of the type sometimes used to analyze political ideology in national legislatures. I show that a state’s pattern of treaty memberships within the regime significantly affects the likelihood that the international community will pursue costly enforcement measures if the state seeks nuclear weapons. The findings in this paper suggest that state interests—as revealed by treaty adherence—can illuminate important new dynamics in international cooperation, with implications for existing theory on the role of international security institutions in constraining state behavior.



  • Chapter 4: The constraining power of the nuclear nonproliferation regime

  • ► Abstract

Do international security institutions actually constrain state behavior? Proponents of these institutions can point to several seeming success stories; relatively few states, for example, have acquired nuclear weapons since the nuclear nonproliferation regime took shape. Skeptics submit that security institutions have no constraining effect: either states only join an organization if they plan to comply anyway, or else states freely violate agreements once they have signed. Existing empirical work is of little help in adjudicating between these views. This chapter examines the effectiveness of the nuclear nonproliferation treaty in limiting the spread of nuclear weapons. Incorporating the factors that drive states to join the nuclear nonproliferation regime, including the role played by the track record of the regime, allows for quantitative tests that distinguish between an effective security institution and a treaty with no teeth. I use a statistical learning method—a support vector machine (SVM)—in the first stage of this analysis, deriving predicted probabilities of state accession. The second stage of the model uses a matching technique to show that membership in the regime makes states significantly less likely to seek nuclear weapons, even when accounting for selection into nonproliferation agreements.



  • ► Project Abstract

    This project examines how the nuclear nonproliferation regime, and international security institutions more generally, affect the behavior of states. These institutions seem to defy existing theory: punishment is difficult and information hard to come by, yet security institutions often boast near-universal membership and seem to enjoy high levels of compliance. I argue that these institutions can effectively constrain state behavior because states use the accession and compliance decisions of others as important clues about the efficacy of an institution and about the underlying policy preferences of members and non-members alike. I test my hypotheses using data on states’ pursuit of nuclear weapons and their membership in the various international agreements that make up the nuclear nonproliferation regime. I not only identify strong support for the constraining power of the nuclear nonproliferation regime, but also find that the decision of a state to seek nuclear weapons is conditioned to a surprising degree on the compliance of the overall population of member states. At the same time, how the international community responds to a state’s nuclear weapons pursuit depends heavily on the extent to which it is embedded within the larger regime complex.

  • Chapter 1: State compliance and the track record of the nuclear nonproliferation regime
  • ► Abstract

    By most theories of international relations, the nuclear nonproliferation regime ought to be a failure: the regime imposes substantial obligations and costs on its membership, punishment of non-compliance is difficult, and information is hard to come by. Yet the nonproliferation regime boasts near-universal membership and seems to enjoy high levels of compliance. Why, then, does the nuclear non-proliferation work? This chapter proposes a new theory of compliance in which a state’s decision to abide by an international commitment is driven by the track record of the institution. Security institutions like the nonproliferation regime are based on a fundamental bargain among member states: each member is willing to comply only so long as others do. There is often significant uncertainty, however, surrounding the compliance behavior of others and the effectiveness of the institution in constraining state behavior. The track record of the institution provides information that helps to resolve this uncertainty. As time passes with few violations, states will in turn be more likely to comply themselves; evidence of rampant noncompliance, on the other hand, will make states more likely to cheat. Analysis of data on nuclear weapons programs between 1968 and 2010 finds that members of the nuclear nonproliferation regime are more likely to pursue nuclear weapons when there have been a greater number of recent violations of the regime. The chapter’s findings have important implications for nonproliferation policy, where long-term, multilateral efforts to bolster the credibility of the nuclear nonproliferation regime have often taken a back seat to short-term, bilateral foreign policy goals.

  • Chapter 2: Breadth versus depth in international security institutions
  • ► Abstract

    Several international security institutions appear both broad and deep—they impose significant obligations on state parties but still enjoy a large membership. This chapter examines this empirical puzzle, theorizing that in some cases—when it is costly both to abstain from and to be found in violation of an agreement—there is no broader versus deeper tradeoff. High obligation may actually be necessary for large membership, because states will only join institutions when they expect other member states to comply. I find that states are more likely to join the nuclear nonproliferation regime when there is a strong track record of compliance with the institution, lending support to this theory. The results in this chapter are important both for theories of institutional design and for policy discussions surrounding the risks of state withdrawal from elements of the nuclear nonproliferation regime.

  • Paper
  • Chapter 3: Regime complexity and the revealed preferences of states
  • ► Abstract
  • International security institutions often lack formal enforcement mechanisms, but this does not mean that violations of international commitments always go unpunished. States that violate treaties routinely face pressure from others to change their behavior, including through sanctions and military attack. But the lack of formal enforcement measures probably does contribute to significant variation in which states are targeted for punishment—enforcement is nearly always at the discretion of the punishing state. Why do some states face punishment while the transgressions of others are overlooked? I argue that enforcing states look to the policy preferences of violators for signals about the likelihood that enforcement will change state behavior and the cost to the international community of allowing the violation to continue. Patterns of institutional membership within a larger regime help to credibly reveal the preferences of state parties. I use data on membership in the various agreements that make up the nuclear nonproliferation regime to derive a new measure of state preferences over nonproliferation policy issues, applying an item-response theory model of the type sometimes used to analyze political ideology in national legislatures. I show that a state’s pattern of treaty memberships within the regime significantly affects the likelihood that the international community will pursue costly enforcement measures if the state seeks nuclear weapons. The findings in this paper suggest that state interests—as revealed by treaty adherence—can illuminate important new dynamics in international cooperation, with implications for existing theory on the role of international security institutions in constraining state behavior.

  • Paper
  • Poster
  • Slides
  • Animated map
  • Chapter 4: The constraining power of the nuclear nonproliferation regime
  • ► Abstract

    Do international security institutions actually constrain state behavior? Proponents of these institutions can point to several seeming success stories; relatively few states, for example, have acquired nuclear weapons since the nuclear nonproliferation regime took shape. Skeptics submit that security institutions have no constraining effect: either states only join an organization if they plan to comply anyway, or else states freely violate agreements once they have signed. Existing empirical work is of little help in adjudicating between these views. This chapter examines the effectiveness of the nuclear nonproliferation treaty in limiting the spread of nuclear weapons. Incorporating the factors that drive states to join the nuclear nonproliferation regime, including the role played by the track record of the regime, allows for quantitative tests that distinguish between an effective security institution and a treaty with no teeth. I use a statistical learning method—a support vector machine (SVM)—in the first stage of this analysis, deriving predicted probabilities of state accession. The second stage of the model uses a matching technique to show that membership in the regime makes states significantly less likely to seek nuclear weapons, even when accounting for selection into nonproliferation agreements.

Publications

The Negotiation Calculus: Why Parties to Civil Conflict Refuse to Talk

2016. International Studies Quarterly.

Why do some parties to intrastate conflict refuse to negotiate? I propose a simple theory of civil conflict in which the act of negotiation itself carries costs and benefits. Several hypotheses follow: parties to civil conflict will avoid negotiation when they (1) fear alienating external supporters or internal constituencies, (2) risk granting legitimacy to their opponents or signaling weakness to other potential claimants, or (3) find it difficult to identify reliable negotiating partners. Empirical tests find support for my argument. My findings suggest that cases exist in which the parties would reach an agreement if only they could overcome the costs of negotiation and engage in talks. Diplomats and mediators should consider the costs and benefits of talks when planning the timing and form of interventions designed to bring parties to the table.

  • ► Abstract

    Why do some parties to intrastate conflict refuse to negotiate? I propose a simple theory of civil conflict in which the act of negotiation itself carries costs and benefits. Several hypotheses follow: parties to civil conflict will avoid negotiation when they (1) fear alienating external supporters or internal constituencies, (2) risk granting legitimacy to their opponents or signaling weakness to other potential claimants, or (3) find it difficult to identify reliable negotiating partners. Empirical tests find support for my argument. My findings suggest that cases exist in which the parties would reach an agreement if only they could overcome the costs of negotiation and engage in talks. Diplomats and mediators should consider the costs and benefits of talks when planning the timing and form of interventions designed to bring parties to the table.

  • Paper
  • Data
  • Slides
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The Canary in the Nuclear Submarine: Assessing the Nonproliferation Risk of the Naval Nuclear Propulsion Loophole

2015. Nonproliferation Review.

The Treaty on the Non-Proliferation of Nuclear Weapons (NPT) allows states to exempt nuclear material from international safeguards for use in nuclear submarine programs. This material, however, could be diverted for nuclear weapons purposes without the knowledge of inspectors, creating a potentially dangerous loophole in the treaty. This paper argues that to exercise the loophole today would amount to admitting a nuclear weapons program, making it a particularly poor pathway to a weapon for a potential proliferant. Still, if states like Brazil ultimately exempt nuclear material from safeguards for a nuclear submarine effort, they could set a dangerous precedent that makes it easier for others to use the loophole as a route to a nuclear weapons capability. There are several policy options available to mitigate the damage of such a precedent; most promising is the prospect of a voluntary safeguards arrangement that would allow international inspectors to keep an eye on nuclear material even after it has been dedicated to a naval nuclear propulsion program.

  • ► Abstract

    The Treaty on the Non-Proliferation of Nuclear Weapons (NPT) allows states to exempt nuclear material from international safeguards for use in nuclear submarine programs. This material, however, could be diverted for nuclear weapons purposes without the knowledge of inspectors, creating a potentially dangerous loophole in the treaty. This paper argues that to exercise the loophole today would amount to admitting a nuclear weapons program, making it a particularly poor pathway to a weapon for a potential proliferant. Still, if states like Brazil ultimately exempt nuclear material from safeguards for a nuclear submarine effort, they could set a dangerous precedent that makes it easier for others to use the loophole as a route to a nuclear weapons capability. There are several policy options available to mitigate the damage of such a precedent; most promising is the prospect of a voluntary safeguards arrangement that would allow international inspectors to keep an eye on nuclear material even after it has been dedicated to a naval nuclear propulsion program.

  • Paper
iran_negotiations.jpg

The Days After a Deal with Iran: Implications for the Nuclear Nonproliferation Regime

2015. RAND Perspective. With Rebecca Davis Gibbons.

This analysis begins by positing that a nuclear agreement is reached between Iran and the United States, Great Britain, France, Russia, China, and Germany (P5+1). One of a series of RAND perspectives on what the Middle East and U.S. policy might look like in “the days after a deal,” this Perspective examines the deal’s implications for the nuclear nonpro- liferation regime. A completed deal with the Iranians represents good news for the nuclear nonproliferation regime overall. An agreement will reassure some states about the effectiveness of the regime and could contribute to stronger IAEA safeguards in the future, offering inspectors a better chance of detecting undeclared nuclear activities. At the same time, however, an agreement will almost certainly allow Iran to maintain a uranium enrichment capability. This may tempt some states to expand their nuclear infrastructure as part of a hedging strategy. A nuclear agreement with Iran also effectively legitimizes a domestic nuclear infrastructure that was built despite Iran being found in noncompliance with its agreements under the NPT. These downsides to a deal could pose additional challenges to the credibility of the nuclear nonproliferation regime and potentially ease the path for nuclear pursuit by other states in the future.

  • ► Abstract

    This analysis begins by positing that a nuclear agreement is reached between Iran and the United States, Great Britain, France, Russia, China, and Germany (P5+1). One of a series of RAND perspectives on what the Middle East and U.S. policy might look like in “the days after a deal,” this Perspective examines the deal’s implications for the nuclear nonpro- liferation regime. A completed deal with the Iranians represents good news for the nuclear nonproliferation regime overall. An agreement will reassure some states about the effectiveness of the regime and could contribute to stronger IAEA safeguards in the future, offering inspectors a better chance of detecting undeclared nuclear activities. At the same time, however, an agreement will almost certainly allow Iran to maintain a uranium enrichment capability. This may tempt some states to expand their nuclear infrastructure as part of a hedging strategy. A nuclear agreement with Iran also effectively legitimizes a domestic nuclear infrastructure that was built despite Iran being found in noncompliance with its agreements under the NPT. These downsides to a deal could pose additional challenges to the credibility of the nuclear nonproliferation regime and potentially ease the path for nuclear pursuit by other states in the future.

  • Paper

Talking Peace, Making Weapons: IAEA Technical Cooperation and Nuclear Proliferation

2014. Journal of Conflict Resolution. With Robert L. Brown.

A growing literature suggests that nuclear assistance from other countries is an important determinant of whether states pursue nuclear weapons. Existing work does not consider, however, the most widely available source of assistance—the Technical Cooperation (TC) program administered by the International Atomic Energy Agency (IAEA). IAEA assistance is an important piece of the nonproliferation regime’s central bargain: member states enjoy nuclear assistance in exchange for agreeing not to seek nuclear weapons. Using a dataset of TC projects since 1972, we examine whether international nuclear assistance is associated with the pursuit of nuclear weapons. We hypothesize that some TC assistance reduces the cost of pursuing nuclear weapons, making weapons programs more likely. We find that receiving TC related to the nuclear fuel cycle is a statistically and substantively significant factor in state decisions since 1972 to seek nuclear weapons, with important implications for existing theories of nuclear proliferation.

  • ► Abstract

    A growing literature suggests that nuclear assistance from other countries is an important determinant of whether states pursue nuclear weapons. Existing work does not consider, however, the most widely available source of assistance—the Technical Cooperation (TC) program administered by the International Atomic Energy Agency (IAEA). IAEA assistance is an important piece of the nonproliferation regime’s central bargain: member states enjoy nuclear assistance in exchange for agreeing not to seek nuclear weapons. Using a dataset of TC projects since 1972, we examine whether international nuclear assistance is associated with the pursuit of nuclear weapons. We hypothesize that some TC assistance reduces the cost of pursuing nuclear weapons, making weapons programs more likely. We find that receiving TC related to the nuclear fuel cycle is a statistically and substantively significant factor in state decisions since 1972 to seek nuclear weapons, with important implications for existing theories of nuclear proliferation.

  • Paper
  • Data
  • Slides

The Determinants of Nuclear Force Structure

2014. Journal of Conflict Resolution. With Erik Gartzke and Rupal N. Mehta.

A substantial literature examines the causes of nuclear proliferation, but few studies have addressed why states decide on a particular portfolio of weapons systems once they have acquired a basic nuclear capability. We advance a portfolio theory of nuclear force structure, positing that states seek a diverse set of capabilities for nuclear deterrence, but that they also face major resource and organizational constraints. A number of factors may help to explain the portfolio of nuclear forces that states ultimately field, including resource availability, experience as a nuclear power, bureaucratic politics, the conventional threat environment, the presence of nuclear rivals, and the maintenance of nuclear alliances. We test the influence of these factors on force structure using a new dataset of nuclear weapons platforms fielded by nine nuclear nations between 1950 and 2000. Our findings represent an important step in understanding the drivers of nuclear behavior after states have joined the nuclear weapons club.

  • ► Abstract

    A substantial literature examines the causes of nuclear proliferation, but few studies have addressed why states decide on a particular portfolio of weapons systems once they have acquired a basic nuclear capability. We advance a portfolio theory of nuclear force structure, positing that states seek a diverse set of capabilities for nuclear deterrence, but that they also face major resource and organizational constraints. A number of factors may help to explain the portfolio of nuclear forces that states ultimately field, including resource availability, experience as a nuclear power, bureaucratic politics, the conventional threat environment, the presence of nuclear rivals, and the maintenance of nuclear alliances. We test the influence of these factors on force structure using a new dataset of nuclear weapons platforms fielded by nine nuclear nations between 1950 and 2000. Our findings represent an important step in understanding the drivers of nuclear behavior after states have joined the nuclear weapons club.

  • Paper
  • Data
  • Slides
  • Visualization

 

Work in Progress

Nuclear Deterrence and the Structure of Nuclear Forces

With Erik Gartzke and Rupal N. Mehta.
Presented at the 2013 ISA Annual Convention and the 2013 MPSA Annual Meeting.

Deterrence theory predicts that nations with nuclear weapons should be less likely to fight. But under what circumstances do nuclear weapons promote peace? Conceptions of what constitutes an adequate nuclear deterrent vary from mere possession of the bomb, to nuclear superiority, to secure second-strike capabilities. This paper argues that an important, but often overlooked, driver of nuclear deterrence is the deployment of a diversified portfolio of nuclear platforms. We examine the empirical relationship between nuclear force structure and deterrence using data on nuclear platforms deployed by all nuclear weapons states between 1950 and 2000, finding that platform diversification is strongly associated with a reduced likelihood of conflict. Indeed, diversified nuclear capabilities seem to trump other conceptions of effective nuclear force structures—including the superiority and survivability of a nuclear arsenal. Our findings are relevant for both the literature on international conflict and the public discourse on nuclear disarmament, arms control, and proliferation.

  • ► Abstract

    Deterrence theory predicts that nations with nuclear weapons should be less likely to fight. But under what circumstances do nuclear weapons promote peace? Conceptions of what constitutes an adequate nuclear deterrent vary from mere possession of the bomb, to nuclear superiority, to secure second-strike capabilities. This paper argues that an important, but often overlooked, driver of nuclear deterrence is the deployment of a diversified portfolio of nuclear platforms. We examine the empirical relationship between nuclear force structure and deterrence using data on nuclear platforms deployed by all nuclear weapons states between 1950 and 2000, finding that platform diversification is strongly associated with a reduced likelihood of conflict. Indeed, diversified nuclear capabilities seem to trump other conceptions of effective nuclear force structures—including the superiority and survivability of a nuclear arsenal. Our findings are relevant for both the literature on international conflict and the public discourse on nuclear disarmament, arms control, and proliferation.

  • Paper

The Changing Face of Nuclear Proliferation

A rich quantitative literature has identified a number of important drivers of nuclear proliferation. Most of this work, however, treats the determinants of proliferation as constant over the entire nuclear age—the factors leading to proliferation are assumed to be the same in 2014 as they were in 1945. But there are reasons to suspect that the drivers of proliferation have changed over this time. The wide availability of nuclear technology and the broad dissemination of nuclear weapons knowledge may have reduced the cost of a nuclear weapons program and the need for proliferating states to rely on foreign assistance. The global strategic environment also has changed since the end of the cold war, potentially making nuclear weapons less desirable as a means of deterring aggression by adversaries. Finally, the nuclear nonproliferation regime—which did not exist in the early years of the nuclear age—now consists of dozens of international agreements that have created a web of obligations, potentially constraining states’ proliferation behavior. To examine how the drivers of nuclear proliferation have changed over time, I adapt a cross-validation technique frequently used in the machine learning literature. I create a rolling window of training data with which statistical models of proliferation are built, and I then test the predictive power of these models against data from other time periods. In effect, I ask how well proliferation behavior in one decade explains proliferation behavior in another. The result of this analysis is a temporal map of how the determinants of proliferation have changed over time, with important implications both for the literature on nuclear proliferation and for policymakers interested in limiting the future spread of nuclear weapons.

  • ► Abstract

    A rich quantitative literature has identified a number of important drivers of nuclear proliferation. Most of this work, however, treats the determinants of proliferation as constant over the entire nuclear age—the factors leading to proliferation are assumed to be the same in 2014 as they were in 1945. But there are reasons to suspect that the drivers of proliferation have changed over this time. The wide availability of nuclear technology and the broad dissemination of nuclear weapons knowledge may have reduced the cost of a nuclear weapons program and the need for proliferating states to rely on foreign assistance. The global strategic environment also has changed since the end of the cold war, potentially making nuclear weapons less desirable as a means of deterring aggression by adversaries. Finally, the nuclear nonproliferation regime—which did not exist in the early years of the nuclear age—now consists of dozens of international agreements that have created a web of obligations, potentially constraining states’ proliferation behavior. To examine how the drivers of nuclear proliferation have changed over time, I adapt a cross-validation technique frequently used in the machine learning literature. I create a rolling window of training data with which statistical models of proliferation are built, and I then test the predictive power of these models against data from other time periods. In effect, I ask how well proliferation behavior in one decade explains proliferation behavior in another. The result of this analysis is a temporal map of how the determinants of proliferation have changed over time, with important implications both for the literature on nuclear proliferation and for policymakers interested in limiting the future spread of nuclear weapons.

Testing the Role of Uncertainty in Conflict

With Erik Gartzke.
Presented at the 2015 ISA Annual Convention, the 2014 Empirical Implications of Bargaining Models (EIBM) workshop, and the 2013 APSA Annual Meeting.

Bargaining theories of international conflict posit that war stems from states’ uncertainty about their rivals’ capabilities or resolve. While theoretically compelling, this model is difficult to test empirically. A direct test of the theory calls for some way to measure a state’s uncertainty about its rival’s capabilities, which has so far eluded international relations scholars. This paper proposes a new measure of state uncertainty, using estimates of states’ military capabilities compiled by non-profit organizations and government agencies. These estimates are often revised as better information becomes available, and the extent to which these estimates change over time is likely to be associated with uncertainty about a state’s capabilities. Using this and related measures of uncertainty, we conduct the first direct tests of whether increased uncertainty is associated with conflict, as bargaining theories of war predict. The findings have important implications for continued efforts to refine rationalist theories of conflict and for our understanding of the underlying causes of war.

  • ► Abstract

    Bargaining theories of international conflict posit that war stems from states’ uncertainty about their rivals’ capabilities or resolve. While theoretically compelling, this model is difficult to test empirically. A direct test of the theory calls for some way to measure a state’s uncertainty about its rival’s capabilities, which has so far eluded international relations scholars. This paper proposes a new measure of state uncertainty, using estimates of states’ military capabilities compiled by non-profit organizations and government agencies. These estimates are often revised as better information becomes available, and the extent to which these estimates change over time is likely to be associated with uncertainty about a state’s capabilities. Using this and related measures of uncertainty, we conduct the first direct tests of whether increased uncertainty is associated with conflict, as bargaining theories of war predict. The findings have important implications for continued efforts to refine rationalist theories of conflict and for our understanding of the underlying causes of war.

  • Paper
  • Slides

In Search of Nuclear Deterrence: The Effect of Nuclear Weapons Range on International Conflict

With Erik Gartzke and Rupal N. Mehta.
Presented at the 2014 ISA Annual Convention.

A vast academic literature has given us a rich theoretical understanding of the effect of nuclear weapons on international conflict, but empirical work on nuclear deterrence has generally yielded weak and often contradictory findings. It thus remains an open question: Do nuclear weapons reduce conventional or nuclear conflict? In this paper, we relax several of the key assumptions made by most quantitative studies of nuclear deterrence—that the arsenals of all nuclear weapons states are equally capable, that all nuclear weapons within a single state have the same capabilities, and that nuclear states can hold every other state at risk with their full arsenal. Most nuclear states also have significant limitations on their ability to project nuclear power beyond their immediate neighborhood, and the threshold for nuclear weapons use may be higher for a state with a handful of weapons than for one with thousands. We build on existing work to develop a theory of nuclear deterrence that takes into account the destructive power that a nuclear state can bring to bear against its adversary. We then test this theory using a new dataset of nuclear forces since 1950 that includes a measure of the range of nuclear weapons. Our findings offer a clearer picture of the role that nuclear weapons play in inviting or limiting international conventional conflict, and have important implications for ongoing policy discussions of nuclear disarmament and changes to nuclear force structures.

  • ► Abstract

    A vast academic literature has given us a rich theoretical understanding of the effect of nuclear weapons on international conflict, but empirical work on nuclear deterrence has generally yielded weak and often contradictory findings. It thus remains an open question: Do nuclear weapons reduce conventional or nuclear conflict? In this paper, we relax several of the key assumptions made by most quantitative studies of nuclear deterrence—that the arsenals of all nuclear weapons states are equally capable, that all nuclear weapons within a single state have the same capabilities, and that nuclear states can hold every other state at risk with their full arsenal. Most nuclear states also have significant limitations on their ability to project nuclear power beyond their immediate neighborhood, and the threshold for nuclear weapons use may be higher for a state with a handful of weapons than for one with thousands. We build on existing work to develop a theory of nuclear deterrence that takes into account the destructive power that a nuclear state can bring to bear against its adversary. We then test this theory using a new dataset of nuclear forces since 1950 that includes a measure of the range of nuclear weapons. Our findings offer a clearer picture of the role that nuclear weapons play in inviting or limiting international conventional conflict, and have important implications for ongoing policy discussions of nuclear disarmament and changes to nuclear force structures.

  • Paper
  • Animated maps

The Nuclear Nonproliferation Regime Complex: A New Dataset

With Shannon Carcelli, Erik Gartzke, and Rebecca Gibbons.
Presented at the 2014 ISA Annual Convention.

Scholars wishing to study the impact of international institutions generally examine the characteristics and membership of a single treaty or set of treaties. But rarely does a single treaty—no matter how important—represent the extent of a state’s international commitments in a particular policy realm. Using membership in a treaty as a proxy for regime embeddedness can complicate inference, since there is likely to be much less variation in the membership of a single treaty than there is in the larger regime. In this paper, we introduce a new dataset that maps the nuclear regime—the 43 institutions, treaties, and agreements that deal with arms control and disarmament, nuclear non-proliferation, nuclear testing, and nuclear security. We argue that regime-level data are more appropriate for studies of the role of international institutions in constraining state behavior than are data focused on an individual treaty or treaties. We illustrate the use of the new dataset by developing a new measure of state embeddedness in the nuclear non-proliferation regime, examining whether regime membership has an effect on states’ propensity for conflict. Our data and findings have important implications for the study of international institutions.

  • ► Abstract

    Scholars wishing to study the impact of international institutions generally examine the characteristics and membership of a single treaty or set of treaties. But rarely does a single treaty—no matter how important—represent the extent of a state’s international commitments in a particular policy realm. Using membership in a treaty as a proxy for regime embeddedness can complicate inference, since there is likely to be much less variation in the membership of a single treaty than there is in the larger regime. In this paper, we introduce a new dataset that maps the nuclear regime—the 43 institutions, treaties, and agreements that deal with arms control and disarmament, nuclear non-proliferation, nuclear testing, and nuclear security. We argue that regime-level data are more appropriate for studies of the role of international institutions in constraining state behavior than are data focused on an individual treaty or treaties. We illustrate the use of the new dataset by developing a new measure of state embeddedness in the nuclear non-proliferation regime, examining whether regime membership has an effect on states’ propensity for conflict. Our data and findings have important implications for the study of international institutions.

  • Paper
  • Animated map

The Determinants of Multilateral Nuclear Assistance

With Robert L. Brown.
Presented at the 2013 MPSA Annual Conference.

The International Atomic Energy Agency (IAEA) is the world’s foremost provider of nuclear assistance, but its contribution is often overlooked by the existing literatures on nuclear proliferation and international organizations. IAEA nuclear assistance is both important in its own right as a potential factor in the proliferation of sensitive nuclear technology, and as a new domain through which to understand how benefits are provided by other international organizations, such as international financial institutions. In this paper, we explore the ways that different principal-agent relationships—as manifested in voting and participation rules, institutional procedures, and other mechanisms of state control—affect the influence of powerful states over the distribution of multilateral assistance. We test our theories using a dataset of all IAEA nuclear assistance projects since 1971. Our findings have important implications for theoretical work on delegation and agency in international organizations, as well as the literature on the drivers of nuclear proliferation. We also offer new points of leverage for policymakers seeking to limit the spread of sensitive nuclear technology.

  • ► Abstract

    The International Atomic Energy Agency (IAEA) is the world’s foremost provider of nuclear assistance, but its contribution is often overlooked by the existing literatures on nuclear proliferation and international organizations. IAEA nuclear assistance is both important in its own right as a potential factor in the proliferation of sensitive nuclear technology, and as a new domain through which to understand how benefits are provided by other international organizations, such as international financial institutions. In this paper, we explore the ways that different principal-agent relationships—as manifested in voting and participation rules, institutional procedures, and other mechanisms of state control—affect the influence of powerful states over the distribution of multilateral assistance. We test our theories using a dataset of all IAEA nuclear assistance projects since 1971. Our findings have important implications for theoretical work on delegation and agency in international organizations, as well as the literature on the drivers of nuclear proliferation. We also offer new points of leverage for policymakers seeking to limit the spread of sensitive nuclear technology.

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The Enemy of My Enemy Is My Friend: Affinity Networks in International Relations

Poster presented at the 2012 Political Networks Conference.

International relations scholars recognize that the extent to which states have common interests is an important factor in explaining international phenomena, from trade flows to membership in international organizations to war. Affinity between states, however, can be a very difficult concept to measure, and so two states’ shared interests often stand as an omitted variable in IR research. What existing measures of affinity there are fail to account for the networked nature of state interactions: states are not merely a series of dyads, but rather form more complicated interconnections. Even if they do not interact directly, a state can use the relationships other states have with the state’s friends and enemies as a signal of the extent to which they share common interests. I derive a new network measure of affinity using data on a state’s willingness to take another state’s side in an international dispute. By revisiting existing studies in international relations that either omit states’ shared interests or use existing affinity measures, I show that the network approach offers significant benefits in explaining international phenomena.

  • ► Abstract

    International relations scholars recognize that the extent to which states have common interests is an important factor in explaining international phenomena, from trade flows to membership in international organizations to war. Affinity between states, however, can be a very difficult concept to measure, and so two states’ shared interests often stand as an omitted variable in IR research. What existing measures of affinity there are fail to account for the networked nature of state interactions: states are not merely a series of dyads, but rather form more complicated interconnections. Even if they do not interact directly, a state can use the relationships other states have with the state’s friends and enemies as a signal of the extent to which they share common interests. I derive a new network measure of affinity using data on a state’s willingness to take another state’s side in an international dispute. By revisiting existing studies in international relations that either omit states’ shared interests or use existing affinity measures, I show that the network approach offers significant benefits in explaining international phenomena.

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