https://phys.org/news/2018-05-smartphone-cool-year.html

But IDC predicted that the smartphone market would reignite next year, growing about 3 percent annually to 1.654 billion in the year 2022.

The "biggest driver" of the downturn last year was said by IDC to be the China market, which it expected to be down 7.1 percent this year after shrinking 4.9 percent last year.