From dwindling oil supplies to massive charitable donations, the wealth of the world's royals is almost always in flux.
On Monday, it was Queen Elizabeth II whose fortune was on the line: The new British government is set to review the Queen's cut of the profits of the Crown Estate after the property portfolio saw a spike in profits. In other words, the monarch could lose several tens of million in the coming years from her wealth of about $500 million.
Below, take a look at 10 of the richest royals in the world, whose personal fortunes were estimated by Forbes.
1. Bhumibol Adulyadej, King of Thailand — $30 billion
Bhumibol Adulyadej, the King of Thailand, is the longest-reigning monarch in Thai history, with an estimated wealth of $30 billion in 2014, according to Business Spectator and Forbes. King Bhumibol's wealth is managed by the Crown Property Bureau. It includes over 3,000 acres of land in central Bangkok and shares in Siam Cement and Siam Commercial Bank. He also owns the 545-carat Golden Jubilee Diamond, the largest cut and faceted diamond in the world.
2. Hassanal Bolkiah, Sultan of Brunei — $20 billion
Hassanal Bolkiah, the Sultan of Brunei, had an estimated wealth of $20 billion in 2011, according to Forbes. His wealth is a result of oil and gas development in Brunei, and he is known for lavish spending: the Sultan reportedly owns more than 600 Rolls-Royces, and his residence — Istana Nurul Iman, the world's largest palace — cost over $350 million.
3. Abdullah bin Abdulaziz Al Saud, Former King of Saudi Arabia — $18 billion
Abdullah bin Abdulaziz Al Saud, the late King of Saudia Arabia, had an estimated wealth of $18 billion in 2011, according him to Forbes, making him the third richest royal in the world before his death on Jan. 23, 2015. When Abdullah took the throne in 2005, the oil-rich country soon began a $26 billion construction project of a city named in his honor.
4. Khalifa bin Zayed al Nahyan, Emir of Abu Dhabi — $15 billion
Khalifa bin Zayed al Nahyan, the President of the United Arab Emirates and the Emir of Abu Dhabi, had an estimated wealth of $15 billion in 2011, according to Forbes. Sheikh Khalifa has amassed a fortune as chairman of the Abu Dhabi Investment Authority, which manages the UAE's excess oil reserves, estimated to be worth up to half a trillion dollars. He is also known for his philanthropy, contributing to state-of-the-art medical facilities and relief organizations.
5. Mohammed bin Rashid al Maktoum, Emir Sheikh of Dubai — $4 billion
Mohammed bin Rashid al Maktoum, Prime Minister of the United Arab Emirates and the Emir Sheikh of Dubai, had an estimated wealth of $4 billion in 2011 , according to Forbes. Sheikh Mohammed is known for his charitable donations, including a gift of $10 billion in 2007 to set up the Mohammed bin Rashid Al Maktoum Foundation, which aims to empower future generations to develop sustainable solutions in the Arab world.
6. Hans Adam II, Prince of Liechtenstein — $3.5 billion
Hans-Adam II, the Prince of Liechtenstein, has an estimated wealth of $3.5 billion in 2011 , according to Forbes. His fortune comes from owning the Liechtenstein Global Trust, the largest family-owned private wealth firm in Europe. Prince Hans-Adam is known for his extravagant art collection on display in the Liechtenstein Museum.
7. Hamad bin Khalifa Al Thani, Former Emir of Qatar — $2.4 billion
Hamad bin Khalifa Al Thani, the former Emir of Qatar and member of the Al Thani Qatari royal family, had an estimated wealth of $2.4 billion in 2011 , according to Forbes. His wealth comes from establishing the Qatar Investment Authority, which manages the country's excess oil and gas reserves. Sheik Hamad is known for establishing the first Arab global news network, Al Jazeera, loaning about $137 million to support the organization.
8. Albert II, Prince of Monaco — $US 1 billion
Albert II, the Prince of Monaco, had an estimated wealth of $1 billion in 2011 , according to Forbes. His wealth includes holdings in the Société des bains de mer de Monaco, a company that manages the riches of the Monte Carlo Casino and Opéra de Monte-Carlo.
9. Shah Karim al-Hussayni, Aga Khan IV of France — $800 Million
Shah Karim al-Hussayni , the Aga Khan IV of France, had an estimated wealth of $800 million in 2011 , according to Forbes. The Aga Khan, who does not rule over a specific geographic territory, is known for extravagant possessions including a lavish yacht club in Sardinia.
10. Qaboos bin Said al Said, Sultan of Oman — $700 Million
Qaboos bin Said al Said, the Sultan of Oman, had an estimated wealth of $700 million in 2011 , according to Forbes. His personal fortune owes to the country's gas and oil sectors. The Sultan is known for his personal financing of several restorations of mosques around the country.
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