Citi has agreed to reduce the company's dividend to just $0.01 a share for the next three years. Shares in the bank, which has $2 trillion of assets, and operations in 100 countries, today shot up more than 40% at one stage as investors bet that the business was not going to fail. The move also helped to boost global markets, including the FTSE 100 index, highlighting just how important the fate of Citi is to the global financial system.