Oops, forgot there is one for USA too, and that has something like this in hardware;
Jan: 1.7M
Feb: 2.1M
Mar: 2.2M
Apr: 1.8M
May: 2.0M
Jun: 2.0M
So there it is a bit higher. In total forUSA+ Jap the hardware is equally selling Jan to other months.
http://www.vgchartz.com/games/userreviewdisp.php?id=261
That is VGChartz LONGEST review. And it's NOT Cute Kitten DS