Incumbent firms in sustainability transitions – Different conceptions, heterogeneous roles and ideal types

• 174 case studies on incumbent firms are reviewed. • An overview of the state of research is given. • A new definition of the term incumbent is formulated. • Six ideal types of incumbent firms are identified. This paper gives an overview of the state of research on the role of incumbent firms in emission-intensive economic sectors (energy supply, transportation, food supply and processing industries) in sustainability transition processes. On the basis of a systematic review of 174 case studies, the paper comes to two conclusions: Firstly, there is a lack of clear definitions and therefore some conceptual confusion regarding the question of what is actually meant by an incumbent. Secondly, the roles of incumbent firms in transition processes are usually heterogeneous, multidimensional, temporally variable and ambiguous in their implications for the transition process. On this basis, the paper makes two conceptual contributions. Firstly, it offers a (new) definition of the term “incumbent firm” that is tailored to transition research and addresses previous conceptual ambiguities. Secondly, it formulates six ideal types of incumbent firms in sustainability transition processes that go beyond dichotomous role attributions and do justice to the ambiguity and temporal dynamics of the activities of incumbents.