A tendency in current policy research is the focus on ideational features of policymaking, i.e. the way ideas, beliefs and language shape policy processes. The impact of the material situation as it exists irrespective of human interpretation, or in other words, the factual problem pressure, is...

The purpose of this paper is to illuminate the geographical diffusion of photovoltaic installations in Germany quantitatively and to test if preexisting photovoltaic systems stimulate further installations nearby; thus we investigate to which extent knowledge flows depend on geographic...