The objective of this project is to explain sub-state territorial reform processes and outcomes. Empirically, the project addresses the puzzle why recent territorial reforms at the county-level in East Germany have displayed stark variation across the different Länder despite similar contextual conditions. Theoretically, this project will conceptualize reforms as multi-stage processes and thus contribute to our understanding of the conditions inducing and explaining the initiation, diffusion and outcomes of reforms. It is the objective of the first SFB phase to offer a systematic explanation of reform initiation, diffusion and outcomes in East Germany while the subsequent project phases will be devoted to developing a more general theory on sub-state territorial reform processes in European countries.