Okay here is all the numbers for Wii Sales from the VG charts site from July 15 to Sep 1:
-------------North America -------Other -------Japan------- Total
Sept 1 ----122,539------ --------97,239----- 49,322----- 269,100
Aug 25 ----101,932 -------------104,390---- 49104------ 255,426
Aug 18 ----99,623 ---------------106,630----- 73,226---- 279,228
Aug 11 ----96,486--------------- 100,630------ 65,341---- 262,457
Aug 5 ------102,599-------------- 95,928------ 63,391----- 261,918
July 28 ------106,197------------- 99,113------ 75,243---- 280,553
July 21 -----109,194-------------- 92,736------- 82,858---- 284,788
July 15 -----101,673-------------- 91,855------ 109,523 ----303,051
Sales generally hover between 260,000 and 280,000 worldwide. In cases where high profile games get released the sales for that region are higher. (MP3 Sept 1 and DQS Jul 15). The average of all the weeks is 274,565 units per week.
It doesn't appear to me that sales are declining accross the board, they seem to be well within an acceptable percentile of the average (less than 20% plus or minus 274,565). This means that supply has likely stayed about the same and that demand is still very high worldwide.
This doesn't mean that demand in Japan is not down. Perhaps it has and Nintendo is wisely diverting shipments to other areas where demand is greater (hence a 122K week in NA). I also read the other day that Nintendo just started selling the Wii in South Africa, meaning there are still markets that Nintendo has yet to tap.
Long and short; Where demand increases, is where supply gets diverted. Where demand decreases is where it comes from.
