I have a blog post I've never quite finished writing, walking through some analysis of the 34,686,770 Amazon reviews in the Stanford SNAP dataset (https://snap.

I have a blog post I've never quite finished writing, walking through some analysis of the 34,686,770 Amazon reviews in the Stanford SNAP dataset (https://snap.stanford.edu/data/web-Amazon.html https://snap.stanford.edu/data/web-Amazon.html, but there's a newer and better one at http://jmcauley.ucsd.edu/data/amazon/ http://jmcauley.ucsd.edu/data/amazon/). Somewhat surprisingly, the median review score is 5, and if you look at median scores for products, the skew is very much left. So, the data pretty much backs up your observation!