(ANSA) - Rome, July 11 - Smartphone sales will reach 1.25 billion units by the end of 2014, while more than 2 billion smartphones will be sold annually by the year 2018, according to estimates released on Friday in a study by ABI Research, an international technology market intelligence company. According to the research, smartphone usage will be double that of PC usage by 2017, growing 12% annually. "Growth is being driven by developing countries," said Nick Spencer, senior practice director at ABI Research. "The most advanced markets, with an average smartphone ownership rate equal to or more than 60%, are already showing a slow down, with worldwide [smartphone ownership] penetration at about 30%". Chinese and Indian producers of low-cost Android smartphones are leading the growth, with distribution of their devices in Africa, Asia, the Middle East and Latin America. According to the research released by ABI, the iPhone 5S is currently the most popular smartphone in the world.