No need to upvote.
I have been using Steem since before the airdrop over the summer and generally just come once or twice a day and upvote quality content, converting anything I earn into Steem Power in the anticipation that SP would earn interest. I have become accustomed to seeing my Steem Power balance increase steadily, my reward for not cashing out. I notice that this has plateaued in the last few weeks. What's the rub?