Between 2001 and 2004, Mattel lost 20% of its share of the worldwide fashion-doll segment to smaller rivals such as MGA Entertainment, creator of a hip new line of dolls called Bratz. MGA recognized what Mattel had failed to—that preteen girls were becoming more sophisticated and maturing more quickly. At younger ages, they were outgrowing Barbie and increasingly preferring dolls that looked like their teenage siblings and the pop stars they idolized. As the target market for Barbie narrowed from girls ages three to 11 to girls about three to five, the Bratz line cut rapidly into the seemingly unassailable Mattel franchise. Mattel finally moved to rescue Barbie’s declining fortunes, launching a brand extension called My Scene that targeted older girls, and a line of hip dolls called Flavas to compete head-on with Bratz. But the damage was done. Barbie, queen of dolls for over 40 years, lost a fifth of her realm almost overnight—and Mattel didn’t see it coming.

A version of this article appeared in the November 2005 issue of Harvard Business Review.