Johnson attributed the brand's struggles to the nature of the toy industry rather than anything Mattel has or hasn't done since sales started to sag. Toys run through cycles, he said, and often lose their "freshness or relevance."
"Things definitely don't last forever, especially in the toy industry," Johnson said.
Though the doll has endured for more than 50 years, Barbie is no exception. Johnson noted that Barbie has gone through periods of weak sales, but "never goes away."
Mattel did not return requests for comment on the brand's declining sales.
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Girls have increasingly turned to arts and crafts, collectible dolls and electronic devices for their entertainment, Johnson said. Though its effect can't fully be calculated, even merchandise related to the Disney film "Frozen" may have grabbed some of Barbie's market share in the past few quarters, said Sean McGowan, analyst at Needham & Co.
Still, "Frozen" was released last November, meaning it couldn't have contributed to all of the down period.
"Barbie was weak even before 'Frozen' was there," McGowan said.
Consumers have not grown weary of all dolls. Sales of Mattel's American Girl brand were up 6 percent in the second quarter, and McGowan said that the overlap in products could have led to one doll carving out the other's market share.
Johnson said he saw no link between rising American Girl sales and declining Barbie sales.