NEW YORK -- A research group says Apple (AAPL) continues to dominate in tablet computers, although its market share is shrinking because of growing competition.

IDC said Thursday that Apple shipped 22.9 million iPads in the October-December quarter, during which it released a smaller version and updated its full-size models. That's growth of 48 percent from the same period a year earlier, but Apple's market share fell to 44 percent, from 52 percent.

Samsung Electronics, maker of the Galaxy line of devices, saw shipments more than triple to 7.9 million. Its market share expanded to 15 percent, from 7 percent. AsusTek, maker of the Transformer line and Google's (GOOG) Nexus 7, also saw shipments and market share increase.

Amazon's share fell despite shipping more Kindle Fires during the quarter.