@apujanata, I believe you might be talking about 8.1 Million shipped (SOLD TO RETAIL) article, like this one, which is quite different than sold to customer, which is what simEx track, and therefore it is much more accurate to use NPD's figure, not publisher's figure (which is always shipped, or sold to retail).
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I believe you might be talking about 8.1 Million shipped (SOLD TO RETAIL) article, like this one, which is quite different than sold to customer, which is what simEx track, and therefore it is much more accurate to use NPD's figure, not publisher's figure (which is always shipped, or sold to retail).