Nick Bilton wrote an article on NYT Bits how Facebook engagement dropped, and works only when you pay. It's a shame. I also have same kind of result. And I also did test. Without paying it's not possible even to reach to your 1% user, who are already subscribed, or liked your page. It's not unintentional algorithm issue, its Facebook's business approach. So Facebook sharing is not as free as it were year ago.