A research firm says that Samsung’s Galaxy S3 overtook Apple’s iPhone 4S as the world’s bestselling smartphone for the first time in the third quarter.

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Boston-based Strategy Analytics said Thursday the S3 shipped 18 million units in the third quarter. Apple’s iPhone 4S, meanwhile, shipped 16.2 million units, as many people likely held off to buy its successor.

Apple launched the iPhone 5 on Sept. 21. Strategy Analytics executive director Neil Mawston says Galaxy’s top position is likely to be short-lived. The iPhone 5 sold an estimated 6 million units in the third quarter, ended on Sept. 30.