This meant a 4.1% decline for the full-year 2018 or a total of 1.4 billion units shipped, the worst year for the industry, IDC said, adding that existing challenging market conditions meant the likelihood of further falls in 2019. Similar figures have been issued by the research outfit, Counterpoint Research.
"Globally the smartphone market is a mess right now," said Ryan Reith, program vice-president with IDC's Worldwide Mobile Device Trackers.
"Outside of a handful of high-growth markets like India, Indonesia, South Korea, and Vietnam, we did not see a lot of positive activity in 2018.
IDC pointed out that in China, which accounts for about 30% of global smartphone consumption, the top four brands - Huawei, OPPO, vivo and Xiaomi - had increased their share of the market to about 78% from 66% the previous year.
But the total China market itself fell by more than 10% from 2017.
Worldwide, the top five smartphone companies increased their shipments from 63% in 2017 to 66% in 2018.
"With replacement rates continuing to slow across numerous markets, vendors will need to find a new equilibrium that balances the latest smartphone features, compelling design, and affordability," said Anthony Scarsella, research manager with IDC's Worldwide Quarterly Mobile Phone Tracker.
"The arrival of both 5G and foldable devices later this year could bring new life to the industry depending on how vendors and carriers market the real-life benefits of these technologies.
"However, we expect these new devices to elevate average selling prices as new displays, chipsets, and radios will bring an increased price to the bill of materials, which will translate to higher price points for consumers.
"To combat this, carriers and retailers will need to fully maximise trade-in offers for older devices as a type of subsidy to push upgrades throughout 2019."