on both the London Stock Exchange (symbol: RIO), under the name "Rio Tinto Plc", and the Australian Securities Exchange (symbol: RIO) in Sydney, under the name "Rio Tinto Limited". The dual-listed company structure grants shareholders of the two companies the same proportional economic interests and ownership rights in the consolidated Rio Tinto, in such a way as to be equivalent to all shareholders of the two companies actually being shareholders in a single, unified entity. This structure was implemented to avoid adverse tax consequences and regulatory burdens. To eliminate currency exchange issues, the company's accounts are kept, and dividends paid, in United States dollars. Rio Tinto is one of the largest companies listed on either exchange. As such, it is included in the widely quoted indices for each market: the FTSE 100 Index of the London Stock Exchange, and the S&P/ASX 200 index of the Australian Securities Exchange. LSE-listed shares in Rio Tinto plc can also be traded indirectly on the New York Stock Exchange via an American Depositary Receipt. As of 4 March 2009, Rio Tinto was the fourth-largest publicly listed mining company in the world, with a market capitalisation around $134 billion. As of mid-February 2009, shareholders were geographically distributed 42% in the United Kingdom, 18% in North America, 16% in Australia, 14% in Asia and 10% in continental Europe. BHP Billiton bid On 8 November 2007, rival mining company BHP Billiton announced it was seeking to purchase Rio Tinto Group in an all-share deal. This offer was rejected by the board of Rio Tinto as "significantly undervalu[ing]" the company. Another attempt by BHP Billiton for a hostile takeover, valuing Rio Tinto at $147 billion, was rejected on the same grounds. Meanwhile, the Chinese government-owned resources group Chinalco and the U.S. aluminium producer Alcoa purchased 12% of Rio Tinto's London-listed shares in a move that would block or severely complicate BHP Billiton's plans to buy the company. BHP Billiton's bid was withdrawn on 25 November 2008, with the BHP citing market instability from the global financial crisis of 2008–2009. Chinalco investment On 1 February 2009, Rio Tinto management announced that they were in talks to receive a substantial equity infusion from Chinalco, a major Chinese state-controlled mining enterprise, in exchange for ownership interest in certain assets and bonds. Chinalco was already a major shareholder, having bought up 9% of the company in a surprise move in early 2008;