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It’s no secret that the iPhone 5s appears to be a bigger hit than its cheaper, more colorful sibling.

A new study suggests that the iPhone 5c is grabbing less share of the iPhone market than Apple’s iPhone 4s did a year ago when it was the mid-range option. The iPhone 5s, by contrast, has grabbed a larger share of the market than the iPhone 5 did in its first full quarter on the market.

The iPhone 5s accounted for 59 percent of October through December U.S. sales, according to a study from Consumer Intelligence Research Partners. That compares to the iPhone 5’s 50 percent of sales when it was the high-end model a year ago.

The iPhone 5c, meanwhile, represented 27 percent of sales, less than the 32 percent that the iPhone 4s had a year ago when it was the mid-range model. CIRP’s findings are based on a survey of 500 buyers of Apple gear during the survey period.

“The design update worked for Apple, since the would-be mid-priced [iPhone] 5 customers seem to have migrated to the higher priced flagship 5s,” CIRP analyst Josh Lowitz said in an email. “The jury is out on how successful the 5c was in attracting new customers, but we do know that Apple increased the average selling price of iPhones overall.”

The study, which appears consistent with anecdotal characterizations of 5c sales, raises an interesting question.

What if Apple had just made the iPhone 5 its mid-range option rather than designing the all-new 5c?

“If the old iPhone 5 had been the mid-priced phone, we expect that it would have sold a higher percentage of iPhones than the 5c did, as previous mid-priced legacy iPhones have,” Lowitz said. “The 5c seems to have been designed to force certain buyers to the 5s.”

The trend toward higher-end models also seems to have taken place on the capacity side, with a greater number of people opting to pay the extra $100 or $200 for models with more storage.