Skippy peanut butter jars now have an inward "dimple" on the bottom to reduce the amount they hold. (Source: CNN)Prices of your favorite grocery items are skyrocketing, but you probably don't know it. Many companies are using a sneaky way to raise prices without driving customers to less expensive brands: they are shrinking their packaging. A jar of Skippy peanut butter, for example, is the same height and circumference it has always been, but now has a hidden, inward "dimple" on the bottom that decreases the amount the jar holds by two ounces. Boxes of breakfast cereal appear to be the same height and width they've always been, but manufacturers have reduced the boxes' depth from front to back, decreasing the amount of cereal they hold. Rolls of Scott toilet tissue contain the same number of sheets as always (1,000), but the length of each sheet has been cut from 4 to 3.7 inches. A "six ounce" can of Starkist Tuna now holds just five ounces. When asked about the shrinkage, most companies point to higher costs for ingredients, manufacturing and fuel. Dan Howard, a marketing professor at Southern Methodist University, says the only way consumers can fight back against this sneaky way of increasing costs is to refuse to buy from manufacturers who engage in this deceptive tactic.