In some demand studies (Lise and Tol, 2002; Maddison,
2001) population and population density were included in the
model specifications. For this dataset, it is not possible to
include population and population density as they are highly correlated. Instead of using both, only population will be
included as a variable (POP). This is used as a proxy for the
number of man-made attractions or for the amount of infrastructure
in each district. The source of the population data is
the state statistical office (Statistisches Landesamt SchleswigHolstein,
2001)