Smartphone sales have declined for the fifth consecutive quarter, making the past year the worst in the history of smartphone shipments, according to new data from research firm IDC.

The data revealed that after a “challenging holiday quarter” at the end of 2018 global smartphone volumes declined 4.1% last year with a total of 1.4 billion units shipped. In the fourth quarter alone, volumes declined 4.9% with 375.4 million units shipped.

And the situation is not expected to get much better this year.

“With challenging market conditions continuing into the first quarter of 2019, the likelihood of a declining market this year becomes more of a reality,” IDC said in its Worldwide Quarterly Mobile Phone Tracker report.

A second research firm, IHS Markit, published its own smartphone sales figures today, and it reported that shipments for the fourth quarter were even worse than IDC’s numbers. Global smartphone shipments reached 365.2 million units in Q4, which is a 5.7% drop over the previous quarter. IHS’s numbers for the full calendar year, however, were better than IDC’s; IHS projects that smartphone shipments declined 2.4% from 1.44 billion units in 2017 to 1.41 billion units in 2018.

The reasons behind the declining sales vary and include lengthening smartphone replacement cycles; increasing penetration levels in many large markets; political and economic uncertainty; and a growing consumer frustration about continuously rising prices.