Re: Externalities?
Yes, external factors are hard to account for. Some of them are covered in confidentiality, like agreements with suppliers. It's not a secret that big retail operations tend to leech their suppliers pretty hard. Tax incentives are usually semi-transparent - public authorities do not like to advertise them, but cannot bury that information completely.
But there is a lot of external factors, for example a number of competitors and local producers leaving the business, that are not directly attributable nor measurable. It may well be that some of the perceived savings are covertly coming from someone else's pocket.