There's no way to judge the proportion of steemians that views a post because steemit is scared that it will make some popular accounts unpopular should they put such measure in place. No one can actually judge the true acceptance of his/her post as steemit currently is. Using a reward system the we all know is some how bias and infiltrated by bid bots and curation trail to judge a post's acceptance is not healthy for the blockchain
Put a view counter in place and let people see the true acceptance of their blog. the view counter may make those posting nonsense and earning high reward to sit up and start posting things of quality because they would want to attract viewers to their post. Reward system alone doesn't depict the true acceptance of a post, install a view counter so everyone can know how their blog is performing and make improvement when necessary
I think this depends on a number of factors - firstly how many followers you have (and how many of them are active and not bots). For example I have just over 1000 follower, and I know that a fair few of them are bots, not active currentlyor have long left the Steem platform. Alsohow many people your followers follow can play a part. Imagine if someone follows your account, but also follows 2000 other Steemians - they are unlikely ot see alot of your content.
The other factor is of course, how many upvotes you recieve (paid or manual) - if you get enough upvotes to get to trending or hot pages then your blog will be seen by more people. I have had a couple of posts make it to trending (of a more niche tag), and it didnt really make a huge difference.
I think it is hard to put a number or 'proportion' of Steemians that will see our posts because of the factors I have listed above, but I think in general the number of views for the majority of accounts is, sadly, very low
unless you get to hot or trending then noone will see it except the people that follow you. The only exception is if someone resteems it then their followers will see it.