NPD doesn't cover Wallmart so...

Total US hardware sales for February-March-April are 1.45 billion $.

Total new hardware sales for Gamestop for the same period are 339 million$.

Gamestop operates 5400 stores around 4000 of which are located in the US.

So roughly 75% of their hardware revenue come from the US that is 254 million$.

That would give them a 17.5% marketshare for the new console business, quite significant and a lot more than 5% some guestimated...

your basing 360/ps3 numbers off of ps2/ds numbers.... wow.... just wow...

It's better than hot air, which is all you've contributed.

Why did you use the last three months and not just use April? We don't really need to know about their typical hardware sales, just about the period regarding GTA IV.  I have no idea if that helps or hurts the number but April is definitely the more relavent piece of information.

Also you really shouldn't round numbers mid-calculation, the hardware revenue is closer to $250.9 million and would be a 17.3% share.  I know it seems like a small difference but the details can be important and it really only takes an extra second to calculate properly.

Finally, please link your sources for NPD and GS data. 

they don't have data for walmart....their estimates still include walmart sales.  it's called extrapolation.

I was actually surprised by my marketshare numbers so I just spent the time parsing BestBuy 4th quarter results ( sadly not same period, it's Jan-Feb-March whereas Gamestore has weird Feb-March-April).
It's hard to dig into Best Buy numbers as they don't separate DVD and CD from gaming.

But for that 3 month period they have roughly 2.3 Billion of US revenue for Gaming +DVD +CDs. For the same period Gamestop would be roughly around 1.5 billions for US revenue ( take or add 100 or 200 millions).

In the end if you remove DVD and CD for BestBuy and used games for Gamestop I woudn't be surprised if their marketshare were quite close from each others....

 On the internet its called wasting bandwidth (or at least it should be)

So why one month NPD data is like God's word, and then the next month it's horribly wrong.  Many people in this world make me laugh and cry at the same time.

I coudn't do it for April only as Gamestop did not release specific financial information for that month. They released information for the financial quarter ending May 3rd.

Gamestop financial information can be found here.

For the total number of US stores you have to do a little research ( they have 5400 now worldwide, they passed 1k over sea like 4 months ago and they have been opening a lot more shops oversea in the quarter so 4k is probably very close to the reality).

For total US Hardware sale for the same period I added data from NPD Feb, March, April. ( search gamasutra site for NPD and you can find that data).

The only way that Gamestop marketshare data could be lower would be if NPD hardware revenue for those 3 months was underestimated which would just be another way for me to drive my point :P

In the last week of Arpil the PS3 and 360 could very well have doubled their sales from the week before. Lets say it was 40k, 40k, 35k, and then 70k, making it 185k for the month, which was what NPD showed, right?

Why is that hard to believe?