“If you associate a positive feeling with trying on clothes, you’ll spend more money to buy them,” says Joan Chrisler, a professor of psychology at Connecticut College.

“The woman who needs a 12 but finds out she can fit into an 8 is going to get a self-esteem boost, even if she knows it’s a gimmick,” Chrisler says.

A self-esteem boost like that might be welcome after watching rail-thin models and celebrities on fashion runways and TV while the size of the average woman has been slowly increasing.

The average U.S. woman today wears a size 14, says the and Human Services. In Calvin Klein’s sizing chart, that would be a 42-inch bust, a 34½-inch waist and 44½-inch hips. Meanwhile, at Kmart, a size 14 has a 40-inch bust, a 33½-inch waist and 43-inch hips.

Clothing brands adjust sizes to help sales