It follows that the added sales consequent upon the opening of a new shop will be largely offset by reduced sales elsewhere, and that any new jobs created in the new shop will be largely offset by job reductions elsewhere.
That being so, why do newspapers and policians leap to welcome developments in the retail sector? The Sunday Herald reports:
SAINSBURY'S IS to create 1300 new jobs in Scotland by next summer as part of a plan to expand its UK floor space by 15%.
The supermarket group, which has completed a successful four-year turnaround plan, said that most of the jobs would come through the openings of two new stores in Strathaven and Prestwick as well as a revamped store at Glasgow's Braehead.
First minister Alex Salmond welcomed the news, predicting that the new investment would provide a "significant boost to the Scottish economy".
He said: "The company's plans to increase its number of Scottish stores and to expand existing outlets will bring new jobs and investment to communities throughout the country."