Not all STEEM is in SP.

If, for example, there is 50% of the STEEM available is in SP, and I buy the other 50% on the open market and power it up, I just entitled myself to half the reward pool. Hence, what was 100% based upon the previous SP is now 50%. And you will only maintain that percentage if you vote your full allotment of VP a day...because the entire ecosystem is voting daily at 100%.

Secondly author reward are 75% of the pool. If there are 100 articles a day, an an example, and you write 3, all things being equal, lets say you get 3% of the total authorship pool. Now what happens when 30,000 articles are written a day? You still going to maintain the same 3% take of the author pool.

Sure in the real world, not all articles are created equal. However, you have around 25K active users a day....think about that number being 250K a day....ever at 3 cents, 5 cents, 20 cents, those 225K minnows are going to start sucking a bigger portion of the authorship pool.

If there is 100,000 SP available a day right now with 25K active users, you dont think the average reward will decease 6 months from now if there are 250K active users even if the pool increase to 110000 SP a day? Of course it will.