Explain this then:
Famitsu and Media Create both have ~60% direct market coverage in Japan and have error margins well over 5 or even 10% and from what I understand the situation of one huge retailer not being involved (as with Walmart in the US) is not the case in Japan so you'd have thought each would be better equiped to track the remainder of the market they do not directly cover.
Personally, and this is just an opinion and in an off-the-record kind of way, looking at month to month trends it definitely seems evident to me that maybe NPD do not get all of their data in by when they have to release it. They always seem to go higher or lower on a title then adjust it back / forward the following month. 2.7m for Brawl last month seemed a little too high - especially with Nintendo saying 1.4m week one but then to drop to ~300k this month is way out of line with everything we have been getting as well as common sense in general. Vegas 2 did 750k last month, 100k this month on NPD. That is an enormous dropoff - down to ~15k a week if you assume a dropoff throughout April. Seems too extreme but then I thought they seemed very high last month. Our COD4 figures have been a lot bigger recently (Game of the Year edition gave a good boost) but they show sales dropping after being huge Jan-Feb and much higher than us.
I dunno, all just seems too random to me. Every other country in the world seems to have regular, fairly predictable sales patterns but NPD just jumps up and down fairly inexplicably. Across all our data, 360 and PS3 had their biggest weeks of the year at GTA launch and saw good increases the week before - this is true across the board. All the big analysts followed our lead in saying 300k+ months for 360 / PS3 (many much higher - we got slated for being so low if anything) and yet NPD data comes in over 100k below. I am well aware they have ~60% direct coverage and I am not accusing them of foul play but something just doesn't add up.
I'd bet a fortune that they will have huge figures for May - despite all indications to me showing that sales have dropped back to pre-GTA IV levels in just one week. Maybe we are missing a trick and for some reason all of our stores follow totally different buying trends, but I'd find that hard to believe.
You know I was thinking something similar, I mean this is pretty early for NPD this month... usually we have to wait till about 2/3rds into the month even when the reporting period ended within the stated month (rather than 3 days being in the month after like this time)
Perhaps this is just because we only see the free figures, maybe those paying for it get a much better representation (without odd dips and spikes)