So if you tabulate market share since the beginning of February:
Sales (Millions) | Market Share | ||||||
As Of | Wii | X360 | PS3 | Total | Wii | X360 | PS3 |
3-Feb | 20.78 | 16.59 | 9.95 | 47.32 | 43.91% | 35.06% | 21.03% |
6-Jun | 27.04 | 18.99 | 13.10 | 59.13 | 45.73% | 32.12% | 22.15% |
It's pretty clear that in 17 weeks, Wii gained roughly 1.8% market share. So 0.1% per week is about right, for the time period between the beginning of February and the beginning of June.
EDIT: Eh, it didn't save some of my table formatting from Excel, but it should be pretty clear.