The worldwide smartphone market grew 42.6% year over year in the third quarter of 2011 (3Q11), despite a slowdown within key mature markets, according to the IDC research group ( Apple slipped to second place among smartphone vendors.

Samsung became the new leader in the worldwide smartphone market, with total smartphone shipments topping the 20 million unit mark for the first time in the company’s history. Apple,after taking the number one spot last quarter from Nokia, slipped to the number two spot worldwide.

But even after relying on the iPhone 4 for five quarters and the iPhone 3G S for nine, demand for the iPhone remained strong enough for Apple to realize double-digit growth year over year. Now that Apple has launched its iPhone 4S and re-priced its older models in multiple countries, Apple stands poised to challenge Samsung for the leadership position

Vendors shipped 118.1 million units in 3Q11 compared to 82.8 million units in the 3Q10, according to IDC. However, the 42.6% growth was lower than the research group’s forecast of 49.1% for the quarter and lower than 2Q11 growth of 66.7%.
Smartphone growth came in lower than expected due to the delayed launch of the updated Apple iPhone, according to IDC. In previous years, the introduction of a new iPhone resulted in a spike in shipment volumes during the third quarter.

Western Europe and the United States, two key regions for the iPhone launch each year, still posted sizable year-over-year gains, but lower than anticipated. Nonetheless, the worldwide market grew by double digits, underscoring the growing popularity of smartphone.

“Samsung’s ascendancy to the leadership position is the direct result of its broad and deep product portfolio,” says Ramon Llamas, senior research analyst with IDC’s Mobile Phone Technology and Trends team. “Ever since the first Galaxy device launched last year, the company has aggressively expanded and refreshed its selection to include the latest innovations and most popular features. At the same time, its line-up of bada-branded smartphones has earned a welcome reception within key markets.”

At the same time, Samsung’s position will be a challenge to maintain, both in the fourth quarter and beyond, he adds. “Apple’s fourth quarter launch of the iPhone 4S and lower pricing of older models will certainly boost volumes, and Nokia’s recent launch of Windows Phone smartphones marks the beginning of a new era for the company,” says Llamas. “While these point to larger volumes in the quarters to come, they will also lead to increased competition.”