I can't agree with you more. This would have been a nice study if it didn't reach any conclusions; just laid the data, pointed out all the possible reasons why their analysis could be wrong and paved the way for a better study.
One example, their data only covers from 1994 to 2011.
PS: Direct link to the study http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1572085