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The Constraining Power of International Treaties: Theory and Methods


We acknowledge the contribution of von Stein (2005) in calling attention to the very real problem of selection bias in estimating treaty effects. Nonetheless, we dispute both von Stein's theoretical and empirical conclusions. Theoretically, we contend that treaties can both screen and constrain simultaneously, meaning that findings of screening do nothing to undermine the claim that treaties constrain state behavior as well. Empirically, we question von Stein's estimator on several grounds, including its strong distributional assumptions and its statistical inconsistency. We then illustrate that selection bias does not account for much of the difference between Simmons's (2000) and von Stein's (2005) estimated treaty effects, and instead reframe the problem as one of model dependency. Using a preprocessing matching step to reduce that dependency, we then illustrate treaty effects that are both substantively and statistically significant—and that are quite close in magnitude to those reported by Simmons.

Corresponding author
Beth A. Simmons is Professor, Department of Government, Harvard University, 1033 Massachusetts Avenue, Cambridge, MA 02139 (
Daniel J. Hopkins is a Ph.D. student, Department of Government, Harvard University, Littauer Center, North Yard, Cambridge, MA 02138 (
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Abadie Alberto. 2002. “Bootstrap Tests for Distributional Treatment Effects in Instrumental Variable Models.” Journal of the American Statistical Association 97: 28492.
Abadie Alberto, and Guido Imbens. 2004. “Large Sample Properties of Matching Estimators for Average Treatment Effects.” jan 04.pdf (July 12, 2005).
Albert A., and J. A. Anderson. 1984. “On the Existence of Maximum Likelihood Estimates in Logistic Regression Models.” Biometrick 71 (1): 110.
Beck N., J. N. Katz, and R. Tucker. 1998. Taking Time Seriously: Time-Series-Cross-Section Analysis with a Binary Dependent Variable. American Journal of Political Science 42 (4): 126088.
Berinsky Adam J. 1999. “The Two Faces of Public Opinion.” American Journal of Political Science 43 (4): 120930.
Christmann Andreas, and Peter J. Rousseeuw. 2001. “Measuring Overlap in Logistic Regression.” Computational Statistics and Data Analysis 37: 6575.
Downs George W., David M. Rocke, and Peter N. Barsoom. 1996. “Is the good new about compliance good news about cooperation?International Organization 50 (3): 379406.
Harding David J. 2003. “Counterfactual Models of Neighborhood Effects: The Effect of Neighborhood Poverty on Dropping Out and Teenage Pregnancy.” American Journal of Sociology 109 (3): 676719.
Heckman James J. 1976. “The Common Structure of Statistical Models of Truncation, Sample Selection and Limited Dependent Variables and a Simple Estimator of Such Models.” The Annals of Economic and Social Measurement 5: 47592.
Heckman James J. 1979. “Sample Selection Bias as a Specification Error.” Econometrica 47 (1): 15361.
Heckman James J., Hidehiko Ichimura, Jeffrey Smith, and Petra Todd. 1998. “Characterizing Selection Bias Using Experimental Data.” Econometrica 66 (5): 101798.
Ho Daniel, Kosuke Imai, Gary King, and Elizabeth Stuart. 2004a. “Matching as Nonparametric Preprocessing for Improving Parametric Causal Inference.” abs/matchup-abs.shtml (January 12, 2005).
Ho Daniel, Kosuke Imai, Gary King, and Elizabeth Stuart. 2004b. “MatchIt: Nonparametric Preprocessing for Parametric Causal Inference, Version 1.0-1.” Harvard University, Cambridge, MA. Computer program available at
Imai Kosuke. 2005. Do Get-Out-The-Vote Calls Reduce Turnout?: The Importance of Statistical Methods for Field Experiments. American Political Science Review 99 (2): 283300.
Imai Kosuke, Gary King, and Olivia Lau. 2005. “Zelig: Everyone's Statistical Software, Version 2.2-2”. Harvard University, Cambridge, MA. Computer program available at
Imbens Guido. 2004. “Nonparametric Estimation of Average Treatment Effects Under Exogeneity: A Review.” Review of Economics and Statistics 86 (1): 430.
King Gary, James Honaker, Anne Joseph, and Kenneth F. Scheve. 2001. “Analyzing Incomplete Political Science Data: An Alternative Algorithm for Multiple Imputation.” American Political Science Review 95 (1): 4969.
King Gary, Michael Tomz, and Jason Wittenberg. 2000. “Making the Most of Statistical Analyses: Improving Interpretation and Presentation.” American Journal of Political Science 44 (2): 4155.
Lee Lung-fei. 1984. “Tests for the Bivariate Normal Distribution in Econometric Models with Selectivity.” Econometrica 52 (4): 84363.
Lee Lung-fei. 2001. “Self-Selection.” In A Companion to Theoretical Econometrics, ed. B. H. Baltagi. Malden, MA: Blackwell Publishers Inc.
Lemke Douglas, and William Reed. 2001. “War and Rivalry Among Great Powers.” American Journal of Political Science 45 (2): 45769.
Liao Tim Futing. 1995. “The Nonrandom Selection of Don't Knows in Binary and Ordinal Responses: Corrections with the Bivariate Probit Model with Sample Selection.” Quality and Quantity 29: 87110.
R Development Core Team. 2004. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. ISBN 3-900051-07-0,
Reed William. 2000. “A Unified Statistical Model of Conflict Onset and Escalation.” American Journal of Political Science 44 (1): 8493.
Rosenbaum Paul E., and Donald B. Rubin. 1984. “Reducing Bias in Observational Studies Using Subclassification on the Propensity Score.” Journal of the American Statistical Association 79 (387): 51624.
Rosenbaum Paul R. 2002. Observational Studies. 2nd ed. New York, NY: Springer Verlag.
Rousseeuw Peter J., and Andreas Christmann. 2004. “The Noverlap Package,” version 1.0–1. Available online at
Sartori Anne E. 2003. “An Estimator for Some Binary-Outcome Selection Models Without Exclusion Restrictions.” Political Analysis 11: 11138.
Schafer Joseph. 2003. “The Mix Package: Estimation/Multiple Imputation for Mixed Categorical and Continuous Data.” (January 14, 2005).
Sekhon Jasjeet S. 2004. “The Varying Role of Voter Information across Democratic Societies.” (February 24, 2005).
Sekhon Jasjeet S. 2005Matching: Multivariate and Propensity Score Matching with Automated Balance Search.” Computer program available at matching.
Sekhon Jasjeet, and Alexis Diamond. “Genetic Matching for Estimating Causal Effects: A New Method of Achieving Balance in Observational Studies.” Presented at the Summer Meeting of the Society for Political Methodology, Tallahassee, FL.
Signorino Curt. 2003. “Structure and Uncertainty in Discrete Choice Models.” Political Analysis 11 (4): 31644.
Simmons Beth A. 2000. “International Law and State Behavior: Commitment and Compliance in International Monetary Affairs. American Political Science Review 94 (4): 81935.
Timpone Richard J. 1998. “Structure, Behavior, and Voter Turnout in the United States.” American Political Science Review 92 (1): 14558.
Vreeland James Raymond. 2003. The IMF and Economic Development. New York: Cambridge University Press.
Winship Christopher, and Robert D. Mare. 1992. “Models for Sample Selection Bias.” Annual Review of Sociology 18: 32750.
Winship Christopher, and Stephen L. Morgan. 1999. “The Estimation of Causal Effects from Observational Data.” Annual Review of Sociology 25: 659707.
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American Political Science Review
  • ISSN: 0003-0554
  • EISSN: 1537-5943
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