Research COT Academic and Economic Studies: Chang 1985 DeRoon Jijman and Veld 2000 Gilbert 1997 Haigh Hranaiova and Overdahl 2005 Hartzmark 1991 Houthakker 1957 Kearns and Manners 2004 Klitgaard and Weir 2004 Murphy and Purcell 1995 Ripple 2006 Tien 2001 Wang 2001 Wang 2002 Wang 2003 Weiner 2003