This book presents a simple geometric voting model for analyzing parliamentary roll call data.

Keith T. Poole is a Professor of Political Science at the University of California, San Diego. He is the author or coauthor of over 40 articles as well as the coauthor of Congress: A Political-Economic History of Roll Call Voting and Income Redistribution and the Realignment of American Politics.

1. Introduction; 2. The geometry of parliamentary roll call voting; 3. The optimal classification method; 4. Probabilistic spatial models of parliamentary voting; 5. Practical issues in computing spatial models of parliamentary voting; 6. Conducting natural experiments with role calls; 7. Conclusion.