On April 29, Kate Middleton ceased to be a commoner and married into one of the oldest and wealthiest royal families still in existence. While the royal family fulfills only a ceremonial role in U.K. politics (and fodder for those keen on fashion or gossip) and Middleton will be assuming no rulership or political power, there is no question that her lifestyle and living conditions are about to change dramatically.

With the royal nuptials still fresh in our minds, it is worth a look at the those surviving royal families that still command significant resources and/or power. Unlike entrepreneurs, these are individuals who owe their wealth to circumstances of birth and the privileges of their position, not to actual talent or effort. Nevertheless, many of them command resources that cannot be ignored.

Thailand Takes the Top Spot- King Bhumibol of Thailand



Thailand's King Bhumibol holds the top spot on top important lists. Not only is Bhumibol the longest-reigning monarch alive today, but he is also the wealthiest. According to Forbes, Bhumibol's fortune is estimated to be worth upwards of US$30 billion, much of that built through investments in native Thai businesses like Siam Cement and Siam Commercial Bank.

Although King Bhumibol has relatively little power as a constitutional monarch, he has intervened in Thai politics many times to help resolve crises and stories of his poor health have led to sell-offs on the Thai Stock Exchange.

Oil Makes the World Go 'Round

The Sultan of Brunei, Hassanal Bolkiah.



Perhaps not surprisingly, a large percentage of the world's richest royals derive their wealth from the natural resources of their country, and oil in particular. The Sultan of Brunei, Hassanal Bolkiah, is estimated to be worth upwards of US$20 billion and is one of the relatively few absolute monarchs still in power. With only about 25 years of estimated oil reserves left, the Sultan has yet to launch any significant attempts to diversify the Brunei economy beyond oil.

In contrast, Sheikh Khalifa bin Zayed Al Nahyan of Abu Dhabi and Sheikh Mohammed bin Rashid Al Maktoum of Dubai have tried to diversify the economies of their emirates. Nevertheless, with almost 10% of the world's oil reserves underlying his wealth, Sheikh Al Nahyan is worth roughly US$15 billion. While the financial crisis has wreaked havoc on Dubai, and the emirate had to call upon help from fellow UAE member Abu Dhabi, Sheikh Al Maktoum is still estimated to have wealth in excess of US$4 billion, and Dubai has emerged as a leading financial and tourist hub for the Mideast.

Saudi Arabia's king also belongs on this list. Another of the relatively few ruling monarchs, King Abdullah Bin Abdul-Aziz is head of a prodigious family and is estimated to be worth about US$18 billion. Though there has been rampant speculation on the health of Saudi Aramco (the state-owned oil monopoly) and the size of its remaining reserves, the Saudi royal family has been quite active in investing much of its oil-generated wealth into other businesses outside the country.

Europe's Old Money

Prince Albert II of Monaco.



Some readers may be surprised that Europe's legacy of monarchs appears rather lower on the list of wealthiest royals. Hans-Adam II of Liechtenstein is said to be worth nearly US$4 billion, with a personal fortune of at least US$2 billion built through business interests like ownership of LGT Bank. Prince Albert II of Monaco (son of American actress Grace Kelly) is likewise a billionaire, with over US$1 billion in wealth.

By comparison, Queen Elizabeth of England and Queen Beatrix come relatively far behind, with estimated net worths of US$450 million and US$200 million respectively. While much of Queen Elizabeth's wealth is in the form of real estate, jewelry and other assets, Queen Beatrix's wealth is comprised largely of real estate and investment holdings in a variety of companies.

Other Stakes of Note

King Mohammed VI of Morocco.



King Mohammed VI of Morocco is reputed to be worth about US$2.5 billion, due in large part to a sizable stake in ONA Group, a Moroccan company with assets including the country's largest phosphate miner. King Mohammed VI has been relatively active in trying to promote greater economic liberty in Morocco and an expanded range of export-oriented businesses.

Last and not least is the Japanese Imperial family. Japan's Imperial Household Agency is relatively tight-lipped about the financial details of the royal family, but it is known that a great percentage of the family's wealth was transformed to the state after World War 2. Nevertheless, the IHA does publish information on the Imperial family's annual personal expenses and that totaled over 324 million yen for fiscal 2011.

The Bottom Line

There is no doubt today that monarchs and monarchies are an anachronism that few people wish to revitalise. Nevertheless, a significant portion of the world's oil is still under the control of monarchs and even many purely ceremonial rulers hold large fortunes. While monarchies are likely to continue to fade into the dustbins of history, perhaps a few more will choose the path taken by the monarch of Thailand and at least attempt to reinvest their wealth into the industries of their own countries.

How do you quantify an absolute monarch's personal wealth?. . . Considering that they have unrestricted access to their countrys' petro-dollar revenues. It's almost impossible to separate the national wealth from the personal wealth of these Arab royals.

In any case Sheikh Khalifa bin Zayed Al Nahyan should be worth far more than $15b. He heads a royal family that reportedly seats on a fortune of almost a trillion dollars. Chai.