Some give priority to integrated ecological economic modelling and assessment as the culmination
of the development of ecological economics to date, whereas others emphasize socio-economic
studies, unequal exchange etc. Such differences are reflected in the different choice of topics for, on the one hand, the collection The Development of Ecological Economics (Costanza et al., 1997b) and, on the other hand, the introductory texts on ecological economics by Martinez-Alier (no year) and So¨derbaum (2000).