Wim Heijman Wageningen University, The Netherlands, E-mail: wim. heijman@wur. nl Generally speaking, externalities occur when a decision causes uncomp- sated costs or benefits to individuals or groups other than the person(s) making the decision. Examples of negative externalities are numerous in the area of the environment and natural resources. Some negative extern- ities result because a particular type of manufacturing technology is used (e. g...