Apple's iPhone shipments are expected to have registered single-digit percentage growth on year in the fourth quarter of 2015, but shipments are likely to drop 5.2-10.1% on year in the first quarter of 2016 as sales of iPhone 6s and 6s Plus both performed weaker than expected, according to Digitimes Research's latest iPhone report. However, the decline rate of iPhone sales in the first quarter of 2016 will be significant lower than orders to OEM iPhone makers and component suppliers for the quarter.

Shipments of iPhone devices grew by an annual growth rate of over 50% from the fourth quarter of 2014 to the second quarter of 2015 after Apple launched its iPhone 6/6 Plus in late September 2014. Although on-year growth slowed to 36% in the third quarter of 2015, sales of iPhone products accounted for over 60% of Apple's total revenues for four consecutive quarters through the quarter.

Digitimes Research attributed the lackluster performance of the iPhone 6s/6s Plus to the impact of their iPhone 6 predecessors, which featured larger screens, and thus attracted high interest among consumers.

Consequently, combined iPhone shipments for the fourth quarter of 2015 and the first quarter of 2016 are likely to lie within a range of 5% up or down as compared to combined shipments the same period of a year earlier, Digitimes Research estimated.

Digitimes Research also found that there was a significant gap between the production volume of iPhone 6s/6s Plus by OEM suppliers and the sales volume of these devices by Apple for the third quarter of 2015 (Apple's fiscal fourth quarter of 2015). As a result, a total of 13-15 million iPhone 6s devices will be booked as deferred sales by Apple for the fourth quarter of 2015 (Apple's fiscal first-quarter 2016).

Given that OEM iPhone orders for the fourth quarter of 2015 totaled over 75 million units, Digitimes Research believes that deferred sales booking will continue in the first quarter of 2016, widening the gap between end-market sales and orders to OEM suppliers for the quarter.