Good question

Q. My girlfriends and I have no idea what our clothing size is these days. Our body types and weights haven't really changed, but the clothing sizes we wear varies depending on the store or the designer. What gives?

A. There are two key factors. First, there are no universal sizing standards in the United States. And, while American women are bigger than they used to be, many merchandisers have failed to adjust sizes according.

Some companies are cutting their sizes bigger out of fear of losing size-sensitive shoppers when their bodies move up a size or two. Other companies work off their own sizing scale in order to cater to their own client niche.

Basically, it's entirely possible for one store's size 8 to be another store's size 6 or size 4. Likewise, it's up to designers and companies to determine what constitutes small, medium, large, and extra large sizes.

For years, the apparel industry followed what's called Voluntary Product Standards, which are sizing guidelines that date back to 1970 and are based on women's body measurements that the Agriculture Department collected in 1939.

But "the industry has moved away from the practice," according to literature published by the American Apparel & Footwear Association in Arlington, Va.

Instead, clothing manufacturers, such as AnnTaylor, The Gap and The Limited are sizing clothes according to who they see as their primary consumer, said Myrna Garner, professor of apparel merchandise and design at Illinois State University. One company might target women who are 5'7", while others focus on women who have more petite frames.

Even within one particular store, figuring out what size you are might send you to the dressing room a few times as sizes sometimes vary by style. Capri pants might be sized different from khakis; straight skirts can be sized different from A-lines.

It seems like some stores have tried to make size selection easier, offering various lengths of pants, for example. At The Gap, jeans and pants come in short, regular and long.

But there's one issue that is harder for clothiers to deal with: vanity.

"We have a problem with vanity sizing," Garner said. "A third of the (female) population is a size 14 or over... As people age, they tend to get bigger but don't want to go up in size, and so the companies just make the clothes a little bigger."

This is why women's sizes vary more than those for men's clothing, which are based on body measurements like waist and neck size and inseam.

Manufacturers are afraid that female customers would be less likely to buy clothes based on body measurements, but that is changing, according to the apparel association.