People are really running with this. This graph doesnt prove anything. You could try to use it to support a certain hypothesis but there are too many problems with the data for an argument resting on the graph to hold any real water.

People arent rating shows based on any clear or agreed upon criterea. Some people give 1 star ratings just to bring down the ratings of shows that they think are rated too highly.

I think it would be interesting to see the data with all of the 1 and 2 star ratings removed.

The show ratings are also based on averaging integers. Can we really say that there are FOUR significant figures in an average of integer values? Every single one of these shows is essentially rated 4 stars except 2012 which you could argue is rated 5 because the band conciously decided to do something with special significance to fans in that year.

An argument could be made for three tiers, but the bottom tier is distributed all across the x axis.

As it is, even the longest gap by far does not result in a sgnificantly lower rating, it isnt even the worst rated show. The third longest gap is the 4th highest rating!