Almost everything during holidays where they always adjust to npd later on. Uk is for 3ds is over tracked hundreds of thousands. PS3 are greatly undertrack like God of War while others are greatly overtracked. There numbers seem to be more of a guessing game based on preorders then anything actual based on sales. I find it strange that there prediction of the game knack sells in the USA where exactly what they predicted it sold almost. The actual sales based on npd where much lower. This all of course just personal observation but I don't believe any company themselves take the sales from this site seriously.

Though I absolutely agree with vgc methodology and ioi's explanation of that, in my opinion it doesn't help that vgc sticks with reporting numbers that are higher precision than the source data can support. The precision of a number should be based on the margin of error of the underlying data, otherwise you are simply making up a level of precision that isn't supported. If the margin is 5%, then sales of 101428 should be reported as 101428 +/- 5071, or simply 100k because you've got a 4 digit margin of error (leaving the 2 most significant numbers as the actual supported data). That's basic statistical and scientific practise, not reporting data at a higher precision than the data can support. The difficulty obviously is working out your error margin

When something is broken, it's not going to get fixed whilst you ignore the problem or make excuses for it. The sales numbers on this site are abominably poor, particularly around the holidays. Sorry, but that is a fact.

ioi can say that the figures are generally within 5% and therefore acceptable, but that is rarely true for the figures provided. Sure, if you look at the cumulative sales (which are regularly adjusted on this site every time the quarterly results get posted by the respective company) now that the Wii, 360 and PS3 have all sold 80million plus, the results may well fall within the 5% error ioi uses in his argument. However, if you look at the numbers on a weekly basis, VGChartz has a very poor track record. If the site was any good at forecasting, we wouldn't be seeing these large adjustments (relative to the quarterly sales). Either the sample being used is unreliable, too small to be representative or both.

ioi deserves a lot of praise for making this site the success it is with a large (and I presume growing) following but the site does need to get better at the sales tracking/forecasting. If it did, I'm sure Sony, Microsoft, Nintendo and many of the big publishers would take it more seriously and ioi would probably be able to reap greater rewards for the extra work that would be involved.

First, I must admit that I don't know a whole lot about statistics. That said, rounding the numbers to an arbitrary direction every time doesn't sound like a sound method, nor does it sound like a convenient one. Who could ever tell which direction to round the numbers each time? A good rule of thumb, and the only rule I know I can trust, is to round the final results only and never round any intermediate results. I suppose you could round intermediate results in some cases but it requires special care so that no accuracy is lost for the final result.

What I don't understand is why ioi is on here downplaying NPD numbers, as they have FAR more data than VGC does. I also don't remember people adding up their numbers and realizing that they were 1M overtracked on anything when compared to shipment data. And to top it off, once NPD comes out, usually we get adjustments within a week or so to at least be inline with their numbers.

It's like Pachter said, this site is freaking awesome when it comes to older data, just not the greatest with the newer data. Not saying they are always wrong with new data, of course, but there's only so much you can do without incredible amounts of data.

You keep going on about this overtracking of the PS3.  What makes you think it's overtracked?

I agree with him but games like God of War which has sold over 5.2 million in 2012 according to Sony PR and its 2013 and this game still hasn't sold above 4.5 million according to vgchartz and the same goes to Uncharted 3 and a few other games. And I really have respect for what ioi has done with this website its absolutely great but then again ioi gets bashed from sites like IGN for not listing their sources. And with all due respect how does he know whether IGN will be around in the next 5 years? IGN has been around a lot longer than VGC and is far more popular than VGC has even been.

Not arbitrary... what i'm saying is... instead of using 238,738 consoles sold W1 use 240k (added 1,262) so next week lets say it sell 132,000 so use 130k (took 2k) (inbalance of 738), and so on... that is because they are not pulling that exact number on statistic they are guessing a range lets say from 200k to 250k and by their method 238,738 is the most representative number for them so they use it...

But if they are 5 or 10% uncertain of it they shouldn't use precision to the last number because the imprecision is of 11,936 to 23,873 so using 240 or even 250k would be better description of the numbers... hope that helped. But in the end that doesn't make much difference.

Actually, we have it at 79.8M for the week announced over 80M shipped.  Depends on how much over 80M is, really.  If it's 80.2M-80.3M, that puts 400K-500K on shelves.  Which I agree seems a little low, unless they shipped more the following week(s) for Black Friday.  But I can see where it could be a few 100Ks overtracked.

Well no matter wht the reason, we here here  on vgc tend to forget its an estimate. I think ioi has given the same reasoning once before. Long story short, the console manufactures and retailers hav a better idea then we do because they ship and recieve the product.  

When i worked for shenker, loading and unloading trucks. i knew how many and how much of wht i was loading. after that, its an estimate.

P.S. FUCK IGN WAHT HAVE THEY DONE LATELY!!!!