One of the specialized groups involved in election methods is the Comparative Representation and Electoral Systems Research Committee [ERSC] of the International Political Science Association [IPSA]. Many ERSC members are interested in proportional representation. Membership is $20 U.S. for 1998-2000. See http://www.sinica.edu.tw/~ljw/esrc.html The IPSA is having its XVIII World Congress in Quebec City, Canada on 1-5 Aug 2000 with 4 ESRC panels. See the html page for a link having more info.
