Re: No one believes IDC
No one believes IDC's figures.
I wouldn't go that far. They, along with all the other research companies, are often guilty of showing bias to those companies who pay for or even commission their reports – in the past IDC has done a lot of business with Microsoft. To find out more about how they collate the numbers you'll have to buy the report. However, in this field, the IDC numbers correlate more with what I see around me than, say, those of Kantar.
Getting real sales figures from companies isn't that easy as, apart from Apple, they don't control the chain from factory to store shelf.