It would be interesting to see some charts. I haven't seen anybody doing them yet.
Here's how you can calculate current percentage: go to http://steemd.com -> divide total_vesting_fund_steem with current_supply (and multiply with 100)
Right now it's 49,830,755 / 53,765,294 * 100 = 92.68 %
That ignores the reward fund.
Yeah, because the question was about Steem Power.
But of course the liquid Steem supply is also an interesting metric. Formula for it is:
current_supply - total_reward_fund_steem - total_vesting_fund_steem = liquid steem supply