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Revealed: The salary of Mukesh Dhirubhai Ambani

Mukesh Ambani, Chairman and Managing Director of Reliance Industries Limited, smiles as he attends a press conference with BP Chairman, Carl-Henric Svanberg and BP Chief Executive Bob Dudley (both not pictured) in central London, on February 21, 2011. British energy giant BP said Monday that it will pay $7.2 billion (5.3 billion euros) to Mumbai-based Reliance Industries for a 30-percent stake in 23 Indian oil and gas blocks. AFP PHOTO/BEN STANSALL

6 trends evident in Bloomberg Billionaires Index

The Bloomberg Billionaires Index tracks the world's 100 richest people—their worth, their age, their portfolios and more. Here's a few things we learned.