This really isn't a new request but now it looks like retailers are finally listening. Here's an article at the Chicago Tribune by Sheya Meierdierks-Lehman:
"Six inches taller and six sizes smaller than the average American woman, mannequins have long reflected body image trends. As the average person's weight continues to increase, models and mannequins represent fewer and fewer American women, which can cause problems for a young woman's self-esteem. Some countries and fashion industry officials are making an effort to set a more realistic example, but many others are less concerned."
Read article.
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