Which border matters most? An analysis of how different types of internal boundaries affect voting behavior

This paper examines the extent to which different types of territorial units influence election results. Therefore, a new concept is proposed as a dependent variable: Rather than considering election results within territorial units such as constituencies or states, this paper analyzes the electoral differences between neighboring units. Consequently, the boundaries between territorial units, instead of the territorial units themselves, serve as the unit of analysis. To measure electoral differences, a modified form of standard deviation similar to the Gallagher index is employed. By creating variables that indicate whether a municipal boundary is congruent with a higher-level territorial boundary, the effects of territorial units on election results can be quantified and compared. The approach is demonstrated using the example of Germany. Electoral differences are particularly pronounced along the former inner-German border. While constituencies play an important role for candidate votes, they are irrelevant for party votes. Rather, increased electoral differences in party votes occur at the borders of states, government districts, and counties.