POLI 100B CONGRESS
Summary of Spatial Voting Theory

1. Assumptions:
   
   
   1. Legislators have Symmetric Single-Peaked Utility functions centered on their ideal points in the Policy Space.
      
      
   2. Legislators vote for the Policy Outcome Closest to them
      
      
2. The number of Policy Dimensions needed to account for roll call voting in a Legislature is usually only 1 or 2 because of Constraint.
   
   Philip E. Converse, "The Nature of Belief Systems in Mass Publics," 1964
   
   
   • "A term like "ideology" has been thoroughly muddied by diverse uses. We shall depend instead upon the term "belief systems" ... We define a belief system as a configuration of ideas and attitudes in which the elements are bound together by some form of constraint or functional interdependence." (p.207)
     
     
   • Constraint Does Not Have to be Strictly Logical - "…few belief systems of any range at all depend for their constraint upon [strict] logic in this classical sense. … What is important is that the elites familiar with the total shapes of these belief systems have experienced them as logically constrained clusters of ideas, within which one part necessarily follows from another." (p.210-211)
     
     
   • From an observer's point of view, constraint means that certain issue positions are bundled together, and the knowledge of one or two issue positions makes the remaining positions very predictable.