When asked if the emergence of new, lower-cost tablets was affecting the success of the iPad this week, Apple Inc. Chief Executive Tim Cook said he wasn't seeing it.

"I looked at the data, particularly in the U.S., on a weekly basis after Amazon launched the Kindle Fire, and I wouldn't -- in my view there wasn't an obvious effect on the numbers plus or minus," Cook said.

But one clear minus was Apple's declining share of the growing tablet market. Despite gang-buster sales last quarter, the iPad has lost more than 10 percentage points of market share to rival Android tablets since the fourth quarter of 2010, according to a new report from research firm Strategy Analytics.

The iPad dropped to 57.6% of the tablets sold during the most recent fourth quarter, from 68.2% a year earlier, while Android rose to 39.1% from 29.0% a year ago, the report said. While Apple shipped 15.4 million iPads during the quarter, Android makers shipped 10.5 million tablets, more than tripling the 3.1 million they shipped a year earlier.

The Android surge was led primarily by tablets from Amazon and Samsung, according to Strategy Analytics' Neil Mawston.

"Android is so far proving relatively popular with tablet manufacturers despite nagging concerns about fragmentation of Android’s operating system, user-interface and app store ecosystem,” Mawston wrote in a release attached to the report.

The report also noted that global tablet shipments rose to 66.9 million units in 2011, nearly quadrupling the 18.6 million shipped in 2010. Devices "shipped" are those that manufacturers sell to retailers, and do not always represent final consumer sales numbers, especially when tablet makers overestimate the demand for their products. But Mawston said the tablet shipment numbers in this case were a fair representation of the number consumers bought.

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-- David Sarno

Image: Tim Perkins checks out the $199 tablet from Amazon.com at a Best Buy store in L.A. Credit: Lawrence K. Ho / Los Angeles Times