Greece’s economic woes should not impact on world trade greatly, the head of Maersk, the world's biggest shipping company, has said.The country only accounts for about 3% of Europe's economy, Eivind Kolling told the BBC.He added that China's trade was developing "healthily" with no real signs of weakness.Mr Kolling also said that Japan's trading with the rest of the world, and particularly its car industry, was getting back to levels seen before March's earthquake and tsunami.