Air to Spare: Why Are Product Bags, Boxes Not Full?

Dec. 3, 2009— -- Everyone has opened a box or bag, only to find that the product purchased doesn't even begin to fill the package.

It raises interesting questions: Why does a vitamin bottle rattle when you shake it? Or why does pasta mix fill only the bottom of the box?

Brian Wansick, a Cornell University professor and author of "Mindless Eating," said studies show consumers are attracted to big boxes and bags, even if they don't actually contain more food.

"One of the things we found ... is that people determine the value of a product based on the size of the package -- the bigger the size of the package, the more value they believe it is," Wansick said.

But Wansick said it is not an evil plot against consumers.

"As Americans, we love a good conspiracy story, but this is one story where there is no conspiracy," Wansick said. "There is actually empty space in these packages ... for our benefit."

By law, manufacturers are not allowed to build a large amount of black space into their packages unless there is a good reason.

It turns out there are lots of good reasons, according to a report by Consumer Reports magazine.

"Slack fill rules state that you can have excess slack fill if it pertains to, say, protecting the contents inside, if it has to accommodate the machinery that actually boxes, bags and bottles this stuff, if it provides some sort of value added quality," said Consumer Reports senior editor Tod Marks.

Frito Lay explained that potato chips are fragile, and all that air in the bag acts as a cushion that keeps them from crumbling.

Potato chips are sold by weight, not volume. So was the weight accurate?

"Don't worry, we found in every instance manufactures were delivering what they promised in terms of the contents, so you are not being shortchanged," Marks said.