It's just Sony fudging the numbers. They knew the October NPD number would be bad and had to do something to dull the news. 

Only fools get suckered by these press statements. 

 Its not necessarily that paying for it.  Its fact that both VGC and NPD extrapolate total sales based on a sampling from a number of retailers.  Extrapolation can be a very difficult thing to do and statistically it is very subject to error.  You can minimize how far off you are by increasing the % sampled and lowering the % extrapolated.

NPD covers most retailers but walmart so they may be around 60% sampled and 40% extrapolated.  VGC is I'm guessing much lower than the 60% sampled.

I'm not saying whether the extrapolation formulas are better at NPD vs VGC but from an objective statistical standpoint, NPD is more likely to be correct based on their sampling rate.  Whether it actually is or not is a subject for a flamewar. 

I'm new at this - but I suppose the best way to re-check the numbers is indeed by using the actual manufacturer shipped data (to retailers) - over the course of the past years.

For example, if a manufacturer made 1000 units for the past 3 years - chances are the sales to actual end users will be around 1000 units per year.

Because like many people have said, and from a business stand point - manufacturers can only make so much if they can't sell product. Same for retailers - eventually they will stop ordering product if it doesn't sell.

Has VGcharts reconciled these figures from publicly available data - especially from financial statements of these public companies?

I am curious.

As much as I love VGChartz (I've been around for about a year now), it is hard for me to believe that the numbers from here are better estimates than NPD.

I think that discrepancies of 20% or less could reflect a margin of error. But 40% or more is very significant and would tell me that VGC needs either a better algorithm or a more diverse set of retailers.

I was pretty amazed (and skeptical) that the 360 had kept up its high weekly sales after Halo 3 week. It looks like my skepticism was well placed. The NPD numbers just make more sense in relation to the 360 from my own anecdotal evidence having visited several stores the past few weeks and talked to the people that work there.

Hopefully, as VGC starts to get more raw data, the numbers will improve.

Also one thing people don't see is even if VGchartz is off by 100-200K, that is well within the margin of error that ioi wants

Oh this can never end well. Why this month? Why this month? Why couldn't we have taken a stand against NPD and them after the holiday season where sales hardly matter. Grr.

 You just answered your own question, don't worry when the quarterly figures come out in a few months we'll know just how accurate we are

The other place where NPD makes ALOT more sense is in the GHIII sales. I was shocked at how high 360 and how low PS2 sales were.

It just makes sense that the PS2 sales are >= 360 sales.

ioi, Does Vgcharts have some comparison data to what NPD has reported, compared to actual manufacturer shipped data - on a quarterly or even yearly basis - even just a simple comparison like:

NPD monthly reported data - compare to - manufacturer yearly or monthly "shipped" data

Since I'm new at this - is NPD statistically accurate? That is, within a certain tolerable range compared to actual manufacturer data?

I hope someone can answer my questions. Thanks.

Well ,its your site and you do as you wish .If you firmly believe this is as you say then kudos to you for keeping your numbers .But dont be surprised if the site gets less credibility .Most people just know NPD has more samples so will believe in their numbers more than in yours ,and they would be objetively right mathematics wise .And if we enter in a war about NPD consciently undertracking consoles ...well it sounds like conspiration theories .I have felt the same way some times with NPD data for the PS3 being very bad but I am only a videogaming and charts fan I can feel it that way and nothing happens ,but if you run a site and want credibility maybe you should stick to official numbers more accurately .I know for you NPD is also estimations and not a gospel ,but for most people those are the official numbers and thats all.