The world's top miner BHP Billiton Tuesday ditched the traditional annual pricing system for iron ore for most of its sales, shaking up a key market for Asia's growth. The landmark move was announced just a day after four Rio Tinto employees were jailed for corruption surrounding last year's failed negotiations with China, which the Shanghai court said had cost the country huge losses. 'BHP Billiton today announced that it had reached agreement with a significant number of customers throughout Asia to move existing iron ore contracts that were previously priced annually onto a shorter term landed price equivalent basis,' BHP said in a statement. 'The agreements reached represent the majority of BHP Billitons iron ore sales volume.' BHP has long been in favour of moving from annual prices, a system used for decades, to a more flexible mechanism. China has emerged as the world's top consumer of iron ore, the basic ingredient of steel used for everything from buildings to cars and appliances. 