Mr. Tidbit just noticed what he thought would be a particularly troublesome example of stealth price increases in the supermarket (those that result from grocery firms quietly shrinking the package size). The object of Mr. Tidbit's concern is Betty Crocker cake mixes, which have gone from 18.25 ounces to 15.25 ounces -- a reduction of 16 percent. (Pillsbury mixes, from Smucker, are still 18.25 ounces, but in the food industry that kind of asymmetry doesn't last long; Pillsbury's could shrink any minute.)
Most other such unheralded price increases don't affect the nature of the product: When the number of Oreos in a package goes down, they're still the same cookies. But when the size of the cake mixes went down, there were some small changes in the ingredients list, the consumer was directed to add more oil and less water, and baking times were reduced. Mr. Tidbit expected that the smaller amount of mix surely would create cake layers that weren't as high.
Imagine his surprise when he prepared a new, smaller mix alongside one of the old, larger mixes he happened to have, and the new-mix cake was as high as the old one. (The small changes they made really worked.) The new cake was, of course, lighter in weight, but since it was just as tall, that meant it was also lighter in texture -- fluffier.
The nutrition information on the box takes account of the smaller amount of mix: It indicates that the new box produces a cake of 10 servings, each using 43 grams of the mix, where the old box made a cake of 12 (43-grams-of-mix) servings (the expected 16 percent reduction). But, Mr. Tidbit notes, you would certainly cut the new cake into the same number of servings that you did the old cake, so each would be "lighter" dietarily -- having, for example, 16 percent less carbohydrate. You might not prefer the lighter, fluffier cake, but it was not the unfortunate result Mr. Tidbit expected.