Published online by Cambridge University Press: 04 January 2017
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.
Author's note: I thank Doug Dion and Chuck Shipan for helpful comments and discussion. Previous versions of this paper were presented at the University of Iowa's Political Science Faculty Workshop and the University of California at Santa Barbara's Political Science Seminar Series. Financial support from the Robert Wood Johnson Foundation is gratefully acknowledged. Any errors or lapses in judgment are solely the author's responsibility. Replication materials are available on the Political Analysis Web site.