Dress Sizes Shrinking As Waistlines Expand

American waistlines have been growing for decades. Bulging bellies now seem as if they're the rule, not the exception.

But, reports CBS News correspondent Kelly Wallace, that doesn't necessarily show in the sizes of clothing, particularly women's wear.

Amid all the controversy surrounding models and whether they're too thin, celebrities are showing up on red carpets wearing size zeroes, even double-zeroes.

"Double-zero works for James Bond, but seems insane for us as females!" chuckled Kate White, Cosmopolitan magazine's editor in chief.

Why are the numbers we see on clothes tags shrinking, while Americans are expanding?

Wallace compared two pair of Gap khakis, one from 1996, the other from this year. Both are a size two. But the waistline on the more recent pair was two inches wider.

A CBS News producer still wears a size four Jill Stuart skirt from 10 years ago, but when she shops today, she's a zero.

It's called "vanity sizing," and White says retailers are doing it because it works.

"As a woman," White said, "if you feel like you can shimmy into a size four with one designer, you're not necessarily going to want the size eight with somebody else, so it forces everybody to play the game."

Pam Klein of Parsons the New School for Design showed us two skirts sold now in different stores, both with the same size on the tag. But one's an inch-and-a-half larger.

The vanity sizing, she said, enables women to lie to themselves: "You can say, 'I can eat that chocolate and I can be a size six.' "

Klein suggested that things might be changing, pointing, for instance, to the Dove ads showcasing women in all different shapes and sizes. But, she says, until women get more comfortable with the size they actually are, retailers will embrace vanity sizing.

"It feels good," Klein observed. "I'd rather be a size 10 then a size 14, and I know that it's the same thing, but when I open the closet in the morning, I'm getting ready and I look at that tag and I'm like, 'Yes. I'm a size 10!' "

Designer Stephanie Hirsch, founder of "Inca," said she hasn't down-sized any of her products. A small is still a small. But her customers demanded an extra-small, and she complied.

"And that's become a really big seller for us," Hirsch said, "as opposed to a medium, (which) was always the biggest seller, and now it's extra-small and small."

Wallace wondered whether we'll ever get back to reality, the day when, in most stores, the tag matches the actual size of the dress?

"I think," White said, "it's gonna be a long time."

Wallace suggested that to find the right fit women should "suspend your vanity if you can. Try on several different sizes, and objectively decide what looks best."