A former IDC researcher:
“So, the mantra became, preserve the growth rates; to hell with the actual numbers. Even the growth rates are fiction. The fudge is in the “others” category, which is used as a plug to make the numbers work out. In fairness, we did do survey work, calling around, and attending white box conferences and venues to try to get a feel for that market, but in the end, the process was political. I used to tell customers which parts of the data they could trust, essentially the major vendors by form factor and region. The rest was garbage.”
So they make shit up.