Citigroup announces a $7.5 billion investment from the Abu Dhabi Investment Authority. Earlier this month Citigroup CEO Charles Prince resigned after announcing the bank faced up to $11 billion in losses. The Abu Dhabi Investment Authority is now the single largest shareholder in Citigroup. Oil-rich countries in the Middle East have been on a shopping spree recently. Earlier this week a private equity company owned by Dubai's ruler bought a stake in the electronics company Sony.