Just wondering, because I was under the impression that retailers don't provide any weekly information anymore.

Its called educated guessing. Same for the Europe and Japanese numbers. It may be fun to create some discussion around, but don't bet your farm on any of these numbers to actually be correct.

 Actually its based on what retailers they do get data from and then extrapolation for the rest

Thats why its an educated guess, they extrapolate from a very small set of data. That doesnt make it any less of a guesstimate.

That's my point, though. I thought retailers don't give out weekly information anymore. That's why NPD is monthly now instead of weekly. How would VGChartz get weekly information?

Uh, yes it does make it less of a guesstimate. Do you have any education in statistics at all? The margin of error drops dramatically and rapidly as your sample size grows. In most cases, 30 samples is enough to regularly get you within 10 percent of the correct answer. 

If you think there is no difference between "just guessing with no data" and "estimating based on some data," then I'm afraid you need to go back to school.  

Yes, I have higher degree of education in statistics. And yes, bad wording on the "less of a guesstimate", I should have probably said that it still makes it a guesstimate, or that doesnt make it a non-guesstimate. That was my point anyway. And if you read my first sentence I did say that is what makes it an educated guess.

Glad to hear we can agree then! Obviously it's just an estimate. So are the NPD's figures. Given that (almost) all VGChartz numbers were within 10 percent of NPD's for the month, I'd say those estimates are getting pretty good. 

Yes, but obviously the npd numbers have an order of magnitude lower error margin (as far as I understand it they have numbers from 60% of the market or something like that). And as I also said previously, VG-Chartz accuracy may be enough to warrant some discussion around the numbers, but don't assume they are correct numbers, since they could very well be off by a significant amount.

I don't think anyone assumes that the numbers are 100% accurate, but Vgcharts tries to get these numbers as accurate as possible.

Also this is the best and most indepth website on sales figures for videogames. No other website even comes close, so really if someone can find a website that offers what they do, and more accurately then please do provide a weblink.