Postal density is a measure that contains two  exogenous cost drivers such as geographic and demographic characteristics of the areas served, and endogenous drivers reflecting the quality of delivery service.
Geographic and demographic characteristics both impact postal density.
mnli hypothesis: Geographic and demographic characteristics both impact postal density. premise: Postal density is a measure that contains two  exogenous cost drivers such as geographic and demographic characteristics of the areas served, and endogenous drivers reflecting the quality of delivery service.