I found this article had some interesting findings and most are pretty logical.

http://cruisefever.net/0822-study-cruises-more-fun-ever-before/

Finding 1 is pretty straight forward and expected.

Finding 2 however might have something to do with the number of first time cruisers having increased. Since first time is usually the best more first time cruisers should yield more 5 star ratings. 

Finding 3 surprised me. I knew Disney had some good ratings but I was surprised to see them at the top.

Finding 4 is expected.

Finding 5 is sort of expected but also a bit of a surprise. The least desirables have been discussed here before. It would be nice if they had included the top 5 rated ports.