| Jabbamk1 said: VGChartz has been known to just make numbers up. For example. VGChartz had 15,000 sales for Dynasty Warriors 8 Empires on PS4 in the USA 2 weeks before the game released because they forgot to update the delayed release date. That shows they made the number up based on a prediction model and no actual retail tracking. Therefore VGChartz can not be compared to NPD, IDG, Gfk or Media Create who base their tracking using POS data, not predicted data or made up data. |
If they have X as their preorder numbers from their direct sources, and they have Y as their sales numbers from their direct sources, they'll have some combination mX+nY as part of their prediction for total sales. And if they forget to update their release dates, then Y=0, and they end up with just mX... which won't be zero. And that is how they can have it show sales numbers prior to release, especially if it's working on only partial data (remember, I haven't accounted for things like correlations - the value of Y would affect m, and the value of X would affect n, for instance).
And of course, if they were merely guessing numbers, they wouldn't have guessed 15,000 for DW8E on PS4, given that even the PS3 version of the original (and the original always sells better than the expansions) only barely broke that number, and the PS4 version of the first expansion did significantly less. So if they were using a method of guessing, that number just doesn't make sense as a guess. But if it's coming from a statistical model combining sales sources, preorders, and trend data, then it makes more sense - very inaccurate data (in this case, their sales source data being zero) fed into the model produces nonsensical results.
Of course, it goes beyond that. They have retail sources A, B, and C, which represent some fraction of the entire retail market. But then, A, B, and C, and the other sources in the market, have different sales patterns to others. So they have to use predictive techniques to estimate what the others would be, using the information they have. And that means that they end up with correlative elements that have human influences, like judging of subgenre. If they notice that their sources do better in musou games, but worse in FPS, than other sources, then they will scale down their musou numbers and scale up their FPS numbers, relative to the regular prediction.
All of the tracking companies do this. And you claim NPD tracks 95% of the market directly. I'm going to challenge you on the assertion, since I can find no source for that claim. I would bet that the assertion comes from a misunderstanding of something NPD claimed at some point - 5% is an important number in standard statistics, and I'm betting that NPD said that their data is 95% accurate - that is, that the official numbers given to their clients (publicly leaked information, you'll notice, doesn't include this sort of information) statistically have a minimised chance of being more than 5% away from the real number... and those official numbers would include error estimates.
What I *have* been able to find is a kind of chinese whispers in values. In 2008, a Gamasutra article speculated a 60-65% retail coverage in the US by NPD, and it was clearly a speculated value, based on wording. Later mentions of NPD's coverage cite 60-65%, literally as "60-65%", without reference to it being speculation, as though it were the official number. My bet is that the 95% number has arisen in the same way - someone proposed that, with (as I recall) Walmart being added to NPD's list of sources, they "probably have something like 95% coverage"... which lost the "probably" and "something like" qualifiers when repeated.
It would be highly inefficient for NPD to collect 95% of all data. No company requires that much accuracy (with 95% of data, with sensible extrapolation, you'd get within something like 0.01% of the real number something like 95% of the time - note the uncertain figures, I'm not wasting my time working out the real numbers). They need ballpark figures (say, within 5%, or maybe within 1%), and NPD are a business, they aren't going to waste resources. So they'll collect a reasonable sample... and that can mean inaccurate numbers, sometimes.
A Sega rep has actually stated that NPD are routinely as much as 30% off in their numbers (see the 4guys1up podcast for 1/1/2010) - they didn't have Walmart at the time, but adding Walmart wouldn't have magically fixed the inaccuracies). In short, what you believe is going on, simply isn't.
