Frankly if you want more accurate numbers, hit the paypal button - the retail coverage will expand faster that way. In reality, the 70k error was an extrapolation error. That means it was more like an average of 17.5k/week off, which is less than 25% of 360 worldwide sales on a weekly basis. In most weeks, I would imagine it is more like 15-20% off worldwide 360 sales.
Fair point about the 70k being just for the USA though. But the USA is 60% of Xbox sales. That would mean the numbers would still be off by less than 3%. With 360 doing consistenly low numbers everywhere but North America, the UK/Ireland, and Australia, I wouldn't expect the margin of error to be to significant, especially since there are no reliable figures for Europe as a whole besides this website.
If you read the methodology section, ioi tries to incorporate additional sales besides USA & Canada for NPD as well - namely Central & South America, which is worth upto 5%.
People are difficult to govern because they have too much knowledge.
When there are more laws, there are more criminals.
- Lao Tzu
