[SMT] subreddit tracking of the 65-70% like phenomenon

It's [semi-]common knowledge that for some reason, posts usually tend to gravitate towards around 65-70% liking them. I have noticed that sometimes, in some subreddits I believe, this phenomenon is less prevalent. I have never seen an explanation for this, so I'm thinking that if someone could make a graph showing the mean and standard deviation of various subreddits' like percentages, it might shed some light on the phenomenon. Surely it can be automated? Maybe also a correlation between adherence to the rule and # of views/votes/karma/post type?