From the NPD thread in the GameCube forum.
- December -
PS2: 1,940,000
GCN: 1,160,000
XBox: 1,080,000
GBA-SP: 2,260,000
(note: Microsoft claimed that they outsold Nintendo by a whopping 500k units in the last two weeks of the month, which was our first indicator that Nintendo was having problems with selling out)
- January 2004 -
PS2: 338,000
Xbox: 192,000
GCN: 131,000
GBA: 299,000
- February 2004 -
PS2: 363,000
Xbox: 204,000
GCN: 137,000
GBA: 353,000
(at which point Nintendo mentioned the problem)
Edit: and in case you were wondering, the "score" so far in America is sitting at...
Cumulative Installed Base
PS2: 22,958,000
Xbox: 8,187,000
GCN: 7,133,000
GBA: 20,601,000
...with an average game ownership-per-console rate of...
PS2: 8.10
Xbox: 6.58
GCN: 6.09
GBA: 3.42
If Nintendo actually had the hardware to meet demand for all this time, they would be closing in on Microsoft's entire "million unit" American lead like it was nothing. But they're still tripping over their own feet. And May (E3) is rapidly approaching. And Wal-Mart is supposedly printing signs, getting ready for an XBox price drop.