[CommonReader]

new research from the Harvard Business Review shows that the aggregate rating of Amazon reviewers are every bit as good as professional book critics

I am apparently too dense to understand this. What exactly is the "aggregate rating" we get from professional critics? Do professional critics in the US hand out points, a sort of Robert Parker (who wants to make us believe that one bottle of wine is 89 points, the other 92 points) for books?
From a professional critic I expect an erudite review, something I rarely get from the Amazon crowd. The Amazon reviews offer a useful range of opinions, the most scathing being often the most useful. I do distrust the "star reviewers". The sheer number of reviews posted by some of them undermines their credibility.