From ZDNet's Adrian Kingsley-Hughes:
The reasons for this, according to IHS Markit's Jusy Hong and Gerrit Schneemann, are predictable – the newer handsets are too expensive and the older handsets aren't going down in price fast enough.
Apple continues to face challenges in terms of unit shipments—a trend that is unlikely to be fixed soon. Apple shipped 35.3 million iPhones in the second quarter, down 14.6 percent from 41.3 million units one year ago.
Apple continues to be more aggressive with its promotional activities, but still faces two key challenges: super-premium pricing for its latest models and insufficient price elasticity in its older models to drive significant additional shipments of two-to-three-year-old devices.
According to the report, Apple is now in fourth place in terms of global shipments, behind Samsung, Huawei, and Oppo. Closing on Apple's position are Xiaomi and Vivo.
My take: Unverifiable. Also unsurprising, given that Apple last week reported June quarter iPhone revenue down 12%. (See Five easy charts.)
BTW: Kingley-Hughes is not a fan, judging from his focus on unit sales and the snarky "Must read" he tucked between the paragraphs: The 2019 iPhone 11 will be annoying, boring, and expensive.
He forgot "ugly."