Apple enjoyed strong iPhone sales through 2015 as iPhone 6 and 6 Plus filled in the gap for large-screen models in the iPhone series. However, the global smartphone market has reached a high level of saturation, and the sales of the follow-up model, iPhone 6s, have been weak. With replacement demand falling, Apple in the first quarter of this year posted its first quarterly drop in iPhone production volume since this smartphone series was introduced in 2007, totaling at 42 million units.