In Australia we call this “skimpflation” because they aren’t shrinking the final product, they’re skimping on ingredients to lower production costs.
It’s the bane of my existence because brands I know and love will change their ingredients without warning and without changing anything on the packaging (sometimes not even changing the ingredients list! If the ingredients list has always just said “starch” they don’t have to change anything going from arrowroot starch to cheaper potato starch)
I have allergies and I’ve bought two boxes of the same product at the same time, and had an allergic reaction to one, but not the other.
I used to always blame it on my housemates not washing the cooking utensils properly, but I now use separate cooking equipment and I clean down the kitchen before I start and cook at odd times so I’m the only one using the kitchen.
I’ve started emailing companies after my allergic reactions to determine if they have changed an ingredient, and 90% of the time they confirm they have changed the ingredients. Usually they put some PR spin on it about the new ingredient being more allergy friendly or sustainable (they don’t clarify “environmentally” so I assume they mean “financially sustainable for the profits of our company”)