PROPORTIONALITY PROFILES OF WEST EUROPEAN ELECTORAL SYSTEMS.

How proportional are the results of electoral systems designed to ensure proportional representation? How large is the deviation from proportionality for relative majority systems? Does a given system favor large, small or medium-sized parties? Are some parties consistently advantaged? Is the system predictable or erratic? Plotting the percentage of seats-percentage of votes ratio versus percentage of votes for all parties, is found to be a simple and yet powerful graphical method to answer such questions. Application of such "proportionality profiles" to West European multi-party systems leads to a typology of electoral systems based on their actual effect (rather than their formal procedure or intended effect). District magnitude, the number of rounds, and nationwide adjustment rules are found to be more important than formal seat distribution rules such as d'Hondt or Sainte-Laguë. [ABSTRACT FROM AUTHOR]