RE: Steem economy is for authors, not investors

you should turn STEEM into SP. This makes you additional 1.5% a year (in 2017) in form of dividends

It's actually a bit higher than that, currently just over 1.9% APR. I crunched the numbers and posted the results:

https://steemit.com/steemit/@preparedwombat/how-much-interest-does-your-steem-power-earn-i-finally-figure-it-out