iPhone 4S Puts Apple Neck-and-Neck With Android

The iPhone 4S, launched in October, has had an "enormous impact" on the U.S. smartphone market, allowing Apple to eat away at Google Android's previously sizable lead, according to new research from Nielsen.

Demand for Apple smartphones increased nearly 20 percent in December, compared to three months earlier, thanks in large part to the iPhone 4S, Nielsen said Wednesday. In October, just 21.5 percent of smartphone buyers chose an iPhone, compared to 44.5 percent who did in December. Further, 57 percent of new iPhone owners surveyed in December said they bought the latest model, the iPhone 4S.

Still, Android is the most popular smartphone platform overall. More than 46 percent of all smartphone owners had an Android-based device during the fourth quarter of 2011, while just 30 percent owned an iPhone, according to Nielsen. But while Google has the top billing in the smartphone market, it lost much of its lead to Apple during the last three months of the year.

In October, before the launch of the iPhone 4S, Apple's market share among recent smartphone buyers was 36 percentage points behind Android, with the iPhone earning just 25.1 percent share, compared to Android's staggering 61.6 percent. By November, the gap narrowed to less than 10 percentage points, as Apple's share jumped to 38.8 percent, while Android's dropped to 48.7 percent. And by December, the gap closed even further, to less than 2.5 percent, with Android taking 46.9 percent and Apple holding 44.5 percent.

Behind Android and iPhone, RIM's BlackBerry held the third spot in the smartphone market during the fourth quarter of the year with 14.9 percent, followed by Windows Mobile, which had 4.6 percent, Nielsen reported. Smartphone platforms Palm, Symbian, and Windows Phone 7 each had less than 1.5 percent.

Nielsen's new data about the smartphone market mirrors released last week by the NPD Group. Apple and Android significantly distanced themselves in 2011 from all other competitors, essentially making the battle for smartphone market share "a 2-horse race," NPD said.