In IL, the company must put a percentage on any ingredient that is part of the product description. (Caterers seem to be exempt so this would not solve the herring problem.) That was how I found out that Pringles is 28% potatoes. Lechora the cookie dough flavors would say what percentage is in there - the problem is that no one sells it in supermarkets (that I recall), only in ice cream stores - and we never get to see the packaging on those.