@diomedes... good try, but not true.
MS counts consoles shipped to retail, they do not ship re-furbs to retailers.
Sony and Nintendo do exactly the same, I think you may however be getting confused with what Sony used to do, which is to count the number of consoles produced. Even that method doesn't count re-furbished models, but it does count any sent out as replacements for unre-furbishable PS2s.
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@difference between shipped sold, it does seems little low to me, but then Xbox 360s have recently had a dmand boom, so it is perfectly possible MS did not catch up properly with demand. I have heard some saying that X360s are scarce in Germany, perhaps it is so in other regions too.