Somewhat relevant:

"Monarchs, more so than other autocrats, tend to develop norms that help elites solve their collective action problem. Such a “political culture” makes monarchs’ commitments credible. Therefore, monarchs should exhibit longer tenures and faster growth than non-monarchs. Time-series cross-sectional analyses corroborate these hypotheses for the Middle East and North Africa between 1950 and 2004. Monarchs are less likely to suffer coups, revolutions, or government crises. Additionally, as oil rents increase in monarchies, they generate higher economic growth - which does not happen in non-monarchies. A case study of Qatar’s political history puts flesh on a theory of monarchical political culture."

http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1548222