Apple's share of the worldwide tablet market has shipped from 68.2% in the second quarter to 50.4% in the third, according to market researcher IDC.
Lead Android tablet maker Samsung has tripled its market share over the third quarter last year to 18%.
While Amazon, which introduced its first Android tablet, the Fire, last year has come from nowhere to 9%.
The chart is rounded out by two others in the Android camp: China's Lenovo and Taiwan's Asus.
The better news for Apple: it's started its fourth quarter with a bang, selling three million iPads in three days on the back of the new mini and the fourth generation iPad.
The worse news: IDC recently said the five-year-old Android had gained 75% worldwide smartphone shipment share.
IDC worldwide tablet shipments third quarter 2012 (millions; preliminary)
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IDC worldwide tablet shipments second quarter 2012 (millions; preliminary)
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