Agricultural Economics Unit Department of Economics and Management University of Helsinki Finland Comparative study in agricultural externalities from empirical point of view: experts’ perspectives, assessment levels, and policy impacts Chen Qiuzhen ACADEMIC DISSERTATION To be presented, with the permission of the Faculty of Agriculture and Forestry of the University of Helsinki, for public examination in Lecture Hall 6, B-Building, Viikki (Latokartanonkaari 7), on April 08, 2016, at 12 o’clock. Helsinki 2016