Since it includes employee, customer and vendor theft (all forms of internal and external theft), misplaced inventory, mis-shipped inventory, faulty inventory control, damaged inventory, etc... it's not that easy to calculate the parts of the sum, let alone reduce total retail shrinkage.
As one definition is “intended sales income that was not and cannot be realized,” I guess one could also inlude buyer's errors and resulting unsold inventory and pricing errors. It's huge.