Can factors like package size increase the volume of product used? Yes says Brian Wansink of the Wharton School of the University of Pennsylvania. He conducted a series of studies both in the lab and in the field and his conclusion is that product usage increases with larger packs. But this relationship only holds true up to a certain point. If the package is too large the tendency to use more reverses says Wansink. The chart shown here illustrates Wansink's findings. For example the difference in volume of Crisco used was significant when small- and medium-sized packages were compared: 99 mL vs 134 mL. But when medium-sized packages were compared to large the difference in volume of Crisco used was insignificant: 134 vs. 124. "Part of the reason acceleration in usage volume occurs is because larger packages are perceived as less expensive to use than smaller packages" Wansink writes. "There is however a limit to how much spaghetti a consumer would want to eat and to how much detergent he or she would want to use. Before package size decisions are made for a given brand a brand manager should determine the size at which a package no longer influences usage volume." For more information on the study phone Wansink at 215/898-6532.