We estimate two models, one with and one without the regional dummy variables. These variables have a value of one if the port belongs to the Hanse, New Hanse, Anglo-Saxon, Latin or New Latin region, respectively, and a value of zero if not. As these dummy variables are mutually exclusive, and to avoid that this pre-specified clustering influences the results and their interpretation, we will first look at the model without these regional variables and use the model with the regional variables to check our findings.