Shipments of iPads fell for a fourth quarter in a row as the overall tablet market shrank, but Apple Inc. remained an industry leader with a 31.9% market share on the strength of its ecosystem, according to data from Canalys.

Apple’s AAPL, -3.17% iPad shipments slid 18% to 21.5 million units in the fourth quarter as global tablet shipments contracted 12% to 67 million units.

“It was always going to be tough for Apple to repeat its stellar performance of fourth quarter 2013, when it introduced the iPad Air. With an iterative product refresh this year, the drive to upgrade iPads was muted,” said Tim Coulling, senior analyst at Canalys, in a report.

Samsung Electronics Co. 005930, -0.33% also saw its shipments fall 24% to 11 million units for a 16.4% share while Amazon.com Inc. AMZN, -1.78% shipped 4 million tablets for a 5.9% share. Lenovo grabbed a 5.5% of the tablet market with 3.7 million units shipped.

Competition in the tablet market is likely to remain intense with large-screen devices attracting the most interest from consumers.

“‘Canalys expects growth in 2015 to come from tablets with screen sizes larger than 8” as vendors look to improve margins and micro-brand players exit the market. Some of this change will be driven by growth of the Windows platform,” said analyst Rushabh Doshi.

PC sales also declined last quarter with shipments dropping 6% to 148 million units as Windows XP upgrades slowed.