DALLAS (CBSDFW.COM) – Clarissa Almaraz is one frustrated shopper. The 30-year-old Dallas resident says having four kids changed her shape, and with it, her clothing size.

“At one store I’m a six, and the other I’m a 12,” said Almaraz.

Most women can relate to her confusion over clothing sizes.  Tammy Kinley, an associate professor of merchandising at the University of North Texas has been studying the phenomenon for years.

“Every manufacturer has a fit model,” explained Kinley.  “They size to the fit model and then scale up and down to get different sizes from that.  That’s why we get lots of variation.”

Professor Kinley has done significant research on “vanity sizing.”  That’s when clothing designers for the most expensive brands label larger sizes with smaller numbers.

“Smaller sizes make us feel better. That is a fact,” said Kinley. “I think women are very willing to spent money for a size number we like.”

The same woman with a 30 to 31 inch waist and 41 inch hips fits into 3 different sizes depending on the brand.  In Guess, she’d need a size 9, at The Limited she’d take a size 10, and at New York and Company or Kenneth Cole she’d wear a size 12.

“I just wish it were consistent,” said Alvarez.  But Professor Kinley says vanity sizing is meant to flatter women, not frustrate them.

“It does make us feel good to be in a smaller number.”

Professor Kinley’s research shows that one number that matters more than the rest, and that’s a woman’s age. After age 40, women are much less likely to be influenced by the number on the label.

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