Yeah, I try to keep my voting mana (or voting power I guess) above 80-85%, but my vote value at 100%, expressed in HP, gets smaller and smaller.
My 100% vote used to be valued at 0.11 HP a few weeks ago, now it's 0.007HP even though I've powered up all my earnings + STEEM I've sold from my Steem power down.
I was under the impression it's because my account is not growing as fast as other HIVE accounts.
It's because the price of HIVE has decreased in the last few days. It will go back up if the price goes up. So the amount of HIVE your vote is worth isn't really changing, it's the fiat equivalent value that is going up and down.