Product shrinkage is a devious, underhanded, and in my opinion exceedingly dishonest way for companies to make bigger profits on their products. The whole thing is really sneaky. If you look back in the recesses of your cupboard, you may find older forms of products than you can compare to newer packaging. You will often find a subtle difference in the numbers on the product's label.
This subject was brought to my mind tonight after I bought some Cinnamon Pop-tarts at Wal Mart. The box was redesigned with a blue background, and said something like "New look... same great taste!" I put up the groceries, then on a suspicious whim took a look at the label. Hmm - 21 ounces total product weight. I grabbed the box by the refrigerator that had a few crumbled shiny wrapped pairs of Pop-tarts left in it... 22 ounces! The Pop-tarts themselves are subtly different in shape too - my trained eye picked it up immediately!
This practice, because of its nature, is most commonly done to food products, but happens elsewhere too. If you see a redesigned package or a "New and Improved" formula - beware - and check the label! The worst thing is that the practice slips by because they don't change the price. The deceived consumer sees the new looking package with the same price tag, and fails to realize that they've been duped by paying the same amount for less product.
Campbell's soup has done this, potato chip manufacturers have done this, diaper amounts have dropped in the (apparently) same sized packages, and now Pop-tarts have shrunk! Many other manufacturers are doing the same thing behind the scenes.
Write the company! Write your congressman (or analagous government representative!) Protest! Riot in the streets! This shrinkage must stop before we're all left paying the same price for empty cans and boxes!