China at the top of the ranking regarding the «population» smartphones
Until at least 2017, the People's Republic of China is expected to remain at the top of the rankings in terms of smartphone usage, as it hosts the largest smartphone "population" in the world.
As mentioned in a related post on the SEPE website, research by Strategy Analytics shows that in second place (2015) are the USA, with India following, showing rapid growth. Specifically, India is expected by 2017 to surpass the USA, taking the second place among the countries with the largest smartphone sales in the world.
Generally, the international smartphone market is expected to see, both this year and throughout 2016, an increase: According to Strategy Analytics, global sales are estimated to exceed 1.5 billion this year, rising to 1.7 billion devices in 2017.
As for China, estimates call for sales of 458 million devices this year, compared to 405 million in 2014 and a forecast of 491 million in 2016. For 2017, the bar rises to 505 million devices. However, in general, signs of fatigue appear in terms of smartphone sales internationally, as the rate of sales growth declines:
For the year 2015, an increase of 13% is expected, while for 2016 the corresponding rate is estimated at 7%, with forecasts for 2017 indicating an increase of only 3%.

source: naftemporiki.gr

