(Telecompaper) The global smartphone market will continue growing until at least 2021, driven by more first-time users and consumers replacing their phones around every two years, according to a new forecast from IDC. After the first year of single-digit growth in unit shipments in 2016, the smartphone market is expected to grow at a CAGR of 3.3 percent in the five years through 2021, the market researcher predicts.