The worldwide smartphone market grew 79.7% year over year in the first quarter of 2011 (1Q11), driven by a combination of vendors releasing highly anticipated models, widespread availability of older smartphones at lower prices, and sustained end-user demand. According to the International Data Corporation (IDC) Worldwide Quarterly Mobile Phone Tracker, smartphone vendors shipped a total of 99.6 million units in 1Q11, nearly double from the 55.4 million units in the first quarter of 2010.