I do love some crazy data :D

Yeah I think the link from dalz below is pointing that way. I'm not a BC coder though and would need a price history table somewhere to get hold of these values. However:

This data was derived from analyzing every fill_vesting_withdraw operation on the Steem blockchain and determining the rate at which each user was able to power down that day. It's not a perfect value obviously and there are variations for many different reasons. src

Seems it's not spot on, but could still be the best place to look.