I don't think there's a system to break down weekly sales by marketshare. There is a record of weekly sales data, so you could do calculations based off of that.
It's a good idea. Try getting in touch with ioi about it if he hasn't read this already. That guy never stops improving this site.

"The worst part about these reviews is they are [subjective]--and their scores often depend on how drunk you got the media at a Street Fighter event." — Mona Hamilton, Capcom Senior VP of Marketing
*Image indefinitely borrowed from BrainBoxLtd without his consent.







