Customer Date Base analysis Compared to Population by town, city , region

We are a Ladies Fashion Wholesale business with Showrooms in Old, NSW, Vic, SA. We have a current Customer base for each State. We are looking to align our Data base with population Data (Analysis to source) want to determine Sales $ per head of Population in each relative Market. Also want to determine market catchments in each State where we have no representation. Therefore highlighting new Customer opportunities.