RE: The Purpose of Flags/Downvotes
After asking the original author (@cpol) about the 15% he explained he got the info from the original white paper. Perhaps things have changed over the many hard forks. Someone like @timcliff may be able to clarify that.
Reply from @cpol:
In the whitepaper look at it: https://steem.io/steem-whitepaper.pdf page 7 at the end of the page in the section "Steem Power (SP)" it says "SP holders also earn new tokens based on the balance of SP that remains vested. SP holders are paid 15%
of the yearly inflation. The amount of new tokens they receive is directly proportional to the amount of SP they hold relative to the total amount of vested SP across all users."
It come up again on page 21 subsection "Current Allocation & Supply" it says: "Of the new tokens that are generated, 75% go to fund the reward pool, which is split between authors and curators. Another 15% of the new tokens are awarded to holders of SP. The remaining 10% pays for the witnesses to power the blockchain."
That means 15% of the reward pool, not interest on the SP itself.
15% would be 150 SP per year per 1000 Steem powered up. Using the 500 SP delegated I mentioned before, that would come out to 6.25 SP growth monthly if it was 15%, not taking into account the compounding affect. As shown in the case of the delegation I have received, it has only grown 1.348 since I received it on 10/06.
Ah, cool. Thanks for clarifying the 15%!