Sovereign wealth funds in third-world countries don't tend to last long. Nauru would still be one if the richest countries on Earth except that the sovereign wealth fund somehow found its way into the pockets of the people tasked with looking after the sovereign wealth fund.
[0] - http://www.arabnews.com/news/458342 [1] - http://www.renewableenergyworld.com/news/2015/01/saudi-arabi... [3] - http://www.amazon.com/Sleeping-Devil-Washington-Saudi-Crude/... [4] - (heartily recommended, although because most of these things are classified, truly it is his word. In his other book about Iran, his conclusion was to bring Iran to the playing table and recognize them as a regional and world power, so it doesn't seem to follow a strictly American narrative, and in my opinion, gives him a bit of credence. Others may beg to differ, I'm not sure.) [5] - https://en.wikipedia.org/wiki/House_of_Saud
The Atlantic. May 2003 http://www.theatlantic.com/magazine/archive/2003/05/the-fall...
"A former CIA operative argues, in an article drawn form his new book, Sleeping With the Devil, that today's Saudi Arabia can't last much longer—and the social and economic fallout of its demise could be calamitous.
Five extended families in the Middle East own about 60 percent of the world's oil.
The Saud family, which rules Saudi Arabia, controls more than a third of that amount.
In the air in Riyadh and Jidda is the conviction that oil money has corrupted the ruling family beyond redemption, even as the general population has grown and gotten poorer; that the country's leaders have failed to protect fellow Muslims in Palestine and elsewhere; and that the House of Saud has let Islam be humiliated—that, in short, the country needs a radical "purification."