Apple Inc. investors have been betting that the pricey new iPhone X will reignite growth for the company’s most important product line.

But estimates from two market-research firms indicate customers are buying the X and a pair of other new offerings at about the same rate as they did with new models in the past two years—which fell short of the iPhone’s 2015 peak.

The iPhone X, iPhone 8 and iPhone 8 Plus combined for 69% of U.S. iPhone sales for the month ended Dec. 3., with the remainder going to older models, according to a survey of 300 iPhone buyers by technology-analysis firm Consumer Intelligence Research Partners.

By comparison, the iPhone 7 and 7 Plus accounted for 73% of all iPhones sold in their first month in 2016, and the iPhone 6s and 6s Plus accounted for 71% in their first month in 2015, the firm’s prior surveys show. Sales of those devices proved to be lackluster. The iPhone 6 and 6 Plus—which were big hits—accounted for 91% of iPhone sales in their first month in 2014.

The survey offers an early glimpse into the sales performance of the most important new iPhone in years. Apple, which bills the iPhone X as the future of the smartphone, gave it a sleek new design with an edge-to-edge display and a three-dimensional camera system that uses facial recognition to unlock the device. It also carries a starting price of $999, half again the price of previous models. Those factors fueled investor hopes for strong iPhone X sales, helping propel Apple’s stock over the past year.