Year	Number	Location
2009	13th	Tsinghua University, Beijing, China
2007	12th	University of Massachusetts, Amherst, Massachusetts, USA	cache
2006	11th	TU Wien, Vienna, Austria
2004	10th	Purdue University, West Lafayette, Indiana, USA	cache
2003	9th	Villa Mondragone, Monte Porzio Catone (Rome), Italy	cache
2001	8th	University of Illinois Urbana-Champaign, Illinois, USA	cache
2000	7th	University of Glasgow, Glasgow, Scotland	cache
1998	6th	Osaka University, Osaka, Japan
1997	5th	Notre Dame University, Indiana, USA	cache
1995	4th	Arizona State University, Arizona, USA
1994	3rd	Portland, Oregon, USA
1993	2nd	University of Leeds, Leeds, United Kingdom
1992	1st	University of Illinois Urbana-Champaign, Illinois, USA