Find the report in your newsagency software that reports on sales and gross profit by floorspace. While I am not sure, I would expect each of the newsagency software systems to offer such a report. Knowing this and comparing it by department and category ought to provide an invaluable insight into the performance of your business.
My experience is that too many business decisions in too many newsagencies are made based on gut feel and not facts.
Knowing the products that contribute beyond the actual cost of floorspace and being able to compare categories and even suppliers will help you better allocate floorspace. I have see newsagents surprised when they see the results for their business.
If you can’t find the report, contact your software company.