VGChartz Hardware data for the period 24th Feb 2007 to 31st Mar 2007:
VGChartz Hardware data for the period 07th Apr 2007 to 12th May 2007:
As you can see, last year the 6 weeks leading up to their fiscal year end had a noticeable smaller shipment than the 6 weeks after their fiscal year end; with how close Nintendo got to their projected shipments many people suggested that Nintendo held back hardware to be released in their next fiscal year.
This year Nintendo forecast 14 Million Wii systems from March 31st 2007 to March 31st 2008, currently they have sold 15.8 Million and will likely pass 17 Million by March 31st. It is possible that Nintendo is limiting the ammount of hardware shipped out in order to stay close to their projection.
Note: You want to stay close to your projection at the end of the year, or to adjust your projection through out the year (so that it will match at the end of the year), otherwise people will distrust your future projections.