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Selection Bias in Comparative Research: The Case of Incomplete Data Sets

  • Simon Hug (a1)


Selection bias is an important but often neglected problem in comparative research. While comparative case studies pay some attention to this problem, this is less the case in broader cross-national studies, where this problem may appear through the way the data used are generated. The article discusses three examples: studies of the success of newly formed political parties, research on protest events, and recent work on ethnic conflict. In all cases the data at hand are likely to be afflicted by selection bias. Failing to take into consideration this problem leads to serious biases in the estimation of simple relationships. Empirical examples illustrate a possible solution (a variation of a Tobit model) to the problems in these cases. The article also discusses results of Monte Carlo simulations, illustrating under what conditions the proposed estimation procedures lead to improved results.



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Achen, Christopher H. 1986. Statistical Analysis of Quasi-Experiments. Berkeley: University of California Press.
Barranco, José, and Wisler, Dominique. 1999. “Validity and Systematicity of Newspaper Data in Event Analysis.” European Sociological Review 15(3): 301322.
Bloom, David E., and Killingsworth, Mark R. 1985. “Correcting for Truncation Bias Caused by a Latent Truncation Variable.” Journal of Econometrics 27:131135.
Breen, Richard. 1996. Regression Models: Censored, Sample Selected or Truncated Data. Thousand Oaks, CA: Sage.
Brehm, John. 1993. The Phantom Respondents. Opinion Surveys and Political Representation. Ann Arbor: University of Michigan Press.
Brehm, John. 2000. “Alternative Corrections for Sample Truncation: Applications to the 1988 and 1990 Senate Election Studies.” Political Analysis 8:183199.
Cohen, Frank S. 1997. “Proportional Versus Majoritarian Ethnic Conflict Management in Democracies.” Comparative Political Studies 30:607630.
Cox, Gary W. 1997. Making Votes Count. Cambridge: Cambridge University Press.
Dion, Douglas. 1998. “Evidence and Inference in the Comparative Case Study.” Comparative Politics 30:127145.
Fearon, James D. 1991. “Counterfactuals and Hypothesis Testing in Political Science.” World Politics 43:169195.
Fearon, James D. 2002. “Ethnic Structure and Cultural Diversity Around the World: A Cross-National Data Set on Ethnic Groups.” Paper prepared for delivery at the 2002 Annual Meeting of the American Political Science Association, Boston, August 29-September 1, 2002.
Fearon, James D., and Laitin, David D. 1997. A Cross-Sectional Study of Large-Scale Ethnic Violence in the Postwar Period. Paper prepared for the conference Cooperation under Difficult Conditions, La Jolla, University of California, San Diego, 1997.
Fillieule, Olivier. 1996. Police Records and the National Press in France: Issues in the Methodology of Data-Collections from Newspapers. Florence, European University Institute. EUI working papers of the Robert Schuman Centre; RSC 96/25.
Geddes, Barbara. 1991. “How the Cases You Choose Affect the Answers You Get: Selection Bias in Comparative Politics.” In Political Analysis, Stimson, James A., ed. Ann Arbor: University of Michigan Press, pp. 131152.
Goertz, Gary D., and Braumoeller, Bear F. 2000. “The Methodology of Necessary Conditions.” American Journal of Political Science 44:844859.
Gurr, Ted Robert. 1993. Minorities at Risk. A Global View of Ethnopolitical Conflict. Washington, DC: United States Institute of Peace Press.
Gurr Ted, Robert, and Moore, Will H. 1997. “Ethnopolitical Rebellion: A Cross-Sectional Analysis of the 1980s with Risk Assessments for the 1990s.” American Journal of Political Science 41:10791103.
Harmel, Robert, and Robertson, John D. 1985. “Formation and Success of New Parties.” International Political Science Review 6:501523.
Heckman, James J. 1976. “The Common Structure of Statistical Models of Truncation, Sample Selection and Limited Dependent Variables and a Simple Estimator for Such Models.” Annals of Economic and Social Measurement 5:475492.
Hug, Simon. 1996. “Altering the Electoral Scene. The Emergence of New Political Parties from a Game-Theoretic Perspective.” European Journal of Political Research 29:169190.
Hug, Simon. 2000. “Studying the Electoral Success of New Political Parties. A Methodological Note.” Party Politics 6:187197.
Hug, Simon. 2001. Altering Party Systems. Strategic Behavior and the Emergence of New Political Parties in Western Democracies. Ann Arbor: University of Michigan Press.
Hug, Simon, and Wisler, Dominique. 1998. “Correcting for Selection Bias in Social Movement Research.” Mobilization 3:141161.
King, Gary. 1989. Unifying Political Methodology: The Likelihood Theory of Statistical Inference. Cambridge: Cambridge University Press.
King, Gary, Keohane, Robert O., and Verba, Sidney. 1994. Designing Social Inquiry. Princeton, NJ: Princeton University Press.
Kitschelt, Herbert. 1988. “Left-Libertarian Parties. Explaining Innovation in Competitive Party Systems.” World Politics 40:194234.
Lijphart, Arend, and Gibberd, Robert W. 1977. “Thresholds and Payoffs in List Systems of Proportional Representation.” European Journal of Political Research 5:219244.
Lustick, Ian S. 1996. “History, Historiography, and Political Science: Multiple Historical Records and the Problem of Selection Bias.” American Political Science Review 90:605618.
Maddala, G. S. 1983. Limited Dependent and Qualitative Variables in Econometrics. Cambridge: Cambridge University Press.
Madow, William G., Nisselson, Harold, and Ingram, eds, Olkin. 1983. Incomplete Data in Sample Surveys. New York: Academic Press.
McCarthy, John D., McPhail, Clark, and Smith, Jackie. 1996. “Images of Protest: Dimensions of Selection Bias in Media Coverage of Washington Demonstrations, 1982 and 1991.” American Sociological Review 61:478499.
Müller-Rommel, Ferdinand. 1993. Grüne Parteien in Westeuropa. Entwicklungsphasen und Erfolgsbedingungen. Opladen: Westdeutscher Verlag.
Muthen, Bengt, and Jöreskog, Karl G. 1983. “Selectivity Problems in Quasi-Experimental Studies.” Evaluation Review 7:139174.
Przeworski, Adam, Alvarez, Michael E., Antonio Cheibub, José, and Limongi, Fernando. 2000. Democracy and Development: Political Institutions and Well-Being in the World, 1950-1990. New York: Cambridge University Press.
Rootes, Chris. 1995. “Environmental Consciousness, Institutional Structures and Political Competition in the Formation and Development of Green Parties.” In The Green Challenge. The Development of Green Parties in Europe, Richardson, Dick and Rootes, Chris, eds. London: Routledge, pp. 232252.
Rosenstone, Steven J., Behr, Roy L., and Lazarus, Edward H. 1984. Third Parties in America. Princeton, NJ: Princeton University Press.
Sigelman, Lee, and Zeng, Langche. 2000. “Analyzing Censored and Sample-Selected Data with Tobit and Heckit.” Political Analysis 8:167182.
Stolzenberg, Ross M., and Relles, Daniel A. 1990. “Theory Testing in a World of Constrained Research Design.” Sociological Methods and Research 35:101132.
Stolzenberg, Ross M., and Relles, Daniel A. 1997. “Tools for Intuition about Sample Selection Bias and Its Correction.” American Sociological Review 62:494506.
Tetlock, Philip E., and Berlin, eds, Aaron. 1996. Counterfactual Thought Experiments in World Politics. Princeton, NJ: Princeton University Press.
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