Another aspect is that a 5% error in Worldwide sales could be a massive error in a specific region.  For example between the time they first went up and now, the rest of the world numbers for the PS4 went up by 24.5k.  That is pretty small for the overall weekly numbers, but represents a 128% increase for the region.

I thought it was already established that VGC numbers were estimates and not an absolute number from every retailer on Earth.

    I was surprised to see ioi's comment earlier.. I usually miss all of his posts here. :/

The problem is, some people seem to think that NPD, or Chart-Track, or Media Create, or Famitsu, etc, are an absolute number from every retailer within their respective regions, rather than using the exact same basic methodology as VGChartz (although certain finer details, especially the specific sources, would vary).

That being said, ioi's comment about "within 5%" is a little concerning, if my memory of statistics is accurate (I'm a pure mathematician, always had some trouble with statistics) - if you have estimated data with a 5% margin of error, and then repeat the "experiment" 100 times, then the margin of error of the final estimate should decrease to far less than 5%. In other words, sales numbers after 2 years should have significantly less than a 5% margin of error if each week's sales number has a margin of error of 5%. In real world context, I'd expect it to reduce less significantly, maybe to 2-3%, given that magnitudes decrease with time (so only the first few data points significantly affect the sum).

What annoys me, though, is people trying to assert that NPD numbers are "right" because they're what publishers use... ignoring the fact that they're the one publishers use because people at NPD have convinced the publishers to use them, just like any other service.

In the past representatives of VGC claimed to work with retailers and have actual access to real life store sales samples, but I wander what happened since then.

My guess is it took too much time to keep those relations active and instead they left the strategy on trying to have their own hard data and instead decided to solely rely on all these alternative methods to estimate sales data (polling, leaderboards, surveys, past sales data, official shipments etc), which IMO works quite well on a consistant basis.

I dont understand the post about error percentages, bell curve analysis, and probability. To me, it seems like a weak attempt at an excuse for publishing bad numbers.  You say you're not "wrong" if you publish 600k and VGC says 485k. That's a 24% error, and a difference of 115k units! How is that even acceptable? As mentioned, it only gets worse as numbers scale higher. A 20% error of 2M is 400k units. That is definitely not meaningless. You're validation for this is that NPD has a margin of error as well, and does the same thing that VGC does? Naturally there's error, but it's going to be much smaller.

And when I look at actual charts, if you want to say the numbers can't be wrong and you're just using probabilities, why are you even publishing these ridiculously precise numbers. What's the difference between saying one game sold 238,854 and another selling 241,913? Heck, what's the point of even publishing the high figures this site does if you're saying they can fall in such a large range? It doesn't take much thought to know a game like GTA is going to sell in the multi-millions. If you're saying the numbers can't be wrong because they fall within a decent portion of a standard distribution, despite being off by a couple million, what's the point?

I don't think the 5% margin is concerning. He said they update accordingly but he is right that 5% is small. Yes it gets a little more tricky as the numbers get larger but it is still pretty close to the actual number.

They offer a good estimation, and all the complaining is silly... the only problem you could argue is LTD being too off after several years of sale, or when official data contradicts this site... both are kinda rare... but bias will make some state over or under tracked to fit their agenda.

Hello ioi im your number 1 fan   :D

The guy was probably taking a shot at you...

But I would agree that if its an estimative it would be easier to see as round numbers 240k... and maybe include a +-% of error in front of the number.