Political Analysis Advance Access originally published online on June 5, 2006
Political Analysis 2006 14(4):421-438; doi:10.1093/pan/mpj014
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The Influence of Unobserved Factors on Position Timing and Content in the NAFTA Vote
Department of Political Science, University of Iowa, 341 Schaeffer Hall, Iowa City, IA 52242, and Department of Health Management and Policy, University of Michigan, 109 Observatory, Ann Arbor, MI 48109
e-mail: boehmke{at}umich.edu
A variety of factors have been shown to influence position timing and the content of positions taken by legislators on important issues. In addition to these observed factors, I argue that unobserved factors such as behind-the-scenes lobbying and party loyalty may also influence position timing and position content. Although hypotheses about observed factors can be tested using traditional methods, hypotheses about unobserved factors cannot. To test for systematic effects of unobserved factors on position timing and content, I develop a seemingly unrelated discrete-choice duration estimator and apply it to data from the vote for the North American Free Trade Agreement. The results indicate that even after controlling for observed factors, there is still evidence that unobserved factors such as Presidential lobbying and/or party loyalty influence both choices.