"Innovation is the lifeblood of retailing, and it's the reason why malls have second lives," he said. New concepts are launched by companies to deal with the changing needs and desires of the consumer, based on everything from the ethnic makeup of the population to shifts in income groups. "The consumer is changing all of the time," Stern said.

One of the ways established retailers deal with the changing customer base is by launching what Stern called "flanker brands," or offshoots of their current chains that might have slightly different characteristics. Examples he gives are Soma, Chico's FAS' lingerie concept for women older than 35 years old; Made Well, a J. Crew chain geared only toward women; and Martin + Osa, American Eagle Outfitters' vehicle to target an older consumer.

Retailers also have concepts specifically for certain age groups. American Girl, Build-A-Bear Workshop and Too Inc.'s Justice chain all cater to girls, while Gap's Forthe & Town and Finish Line's Paiva, are more geared toward women over 35, Stern said.