The package went from 12 ounces to 11.5 ounces. The front of the package says the net weight is 11.5, but on the back the recipe for chocolate chip cookies calls for 12 ounces. It looks like somebody forgot to change the recipe. One product that hasn't shrunk and is proud of it. These days, it seems, not shrinking is a reason to boast.
Consumer Reports publishes examples of shrinking products that people send in.
Include the package, the new one and the old one if you have it, along with any receipts you might have.