Do we need an adjustment?

[Billy D]

In June 2008, I noticed that VG Chartz estimations had the Wii overtracked by 54,000 units when compared to NPD data.

Also that the X-Box 360 was overtracked by 42,000 units and the PS3 was undertracked by 74,000 units.

http://news.vgchartz.com/news.php?id=1536

Moving forward to July it looked as though X-box 360 was set to make a very big comeback. It was no surprise to many people who visit this site or follow gaming in general. A clearance sale on the 20 gig X-Box pro had surely helped the 360 to surge past the PS3 in sales.

However, NPD results for July indicate that VG chartz estimations for that month: had the X-Box 360 overtracked by 138,767 units and the PS3 undertracked by 25,679 units.

http://news.vgchartz.com/news.php?id=1674

No disrespect to the staff at VG charts; we all understand that they can only make educated predictions about sales, but why is it that these predictions seem to favor the 360 over PS3, for the past few months, consistantly?

If the NPD indications are correct one can conclude that for all of 2008 Playstation 3 has outsold X-Box 360 in North America in addition to worldwide.

It is possible that VG Chartz numbers could be more accurate then NPD's, but in my opinion that's not very likely.