The big problem with most analyst estimates on the tablet market is they cover shipments, not sales. It’s a point we regularly make when covering these stories, but it’s worth repeating. Shipments, not sales.

Witness IDC’s latest figures for tablet shipments in Q3 2012, where the company claims overall shipments of 27.8m tablets, up 49.5% year-on-year.

IDC reckons Apple’s iPad took a 50.4% market share ahead of Samsung (18.4%), Amazon (9%) and Asus (8.6%), with the latter including Google’s Nexus 7. Much of the coverage of IDC’s announcement has focused on iPad’s slide in market share to a point where it’s only barely hovering above 50%.

Shipments, not sales, though. While Apple regularly reiterates that it’s making iPads as fast as it can sell them, it’s unclear how many of the Android tablets are sitting on shelves or in distribution centres.

Which is not to say the Android tablet market isn’t growing – it most certainly is, thanks to Amazon and Google/Asus – but that getting accurate numbers on which tablets are actually in use is still difficult.