Last fall’s arrival of the iPhone 5c is having an interesting effect on iPhone sales overall. Apple’s colorful mid-priced handset is causing more customers to select the more expensive iPhone 5s, according to a study from Consumer Intelligence Research Partners (CIRP).

As first noted by Re/Code, CIRP found that through December, the iPhone 5s accounted for 59 percent of U.S. iPhone sales. This compared to 27 percent for the iPhone 5c. During the same period of 2012, the iPhone 5 garnered 50 percent of sales, while the iPhone 4s represented 32 percent.

At one time, Apple sold one new iPhone alongside two previous models. That all changed in 2013 when both the iPhone 5s and iPhone 5c were released. These new phones were joined by the iPhone 4s, which was first released in 2011.

CIRP analyst Josh Lowitz notes:

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. 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.

It will be interesting to see what happens to iPhone sales between now and when Apple announces its next wave of handsets. Traditionally, iPhone sales slow down during the first two quarters of the year. Will buyers continue preferring the iPhone 5s over the iPhone 5c, or will the mid-priced model take the lead? Time will tell.

See also: Foxconn Is Said To Have Shipped 1.4 Million iPhone 5s Handsets To China MobileApple Tops A New Survey Of The Best Smartphones, Tablets And Laptops Of The Past Year, and Looks Like Samsung Will Be Copying Apple Again When They Release The Galaxy S5.