china now top trader with japan china overtook the us to become japan s biggest trading partner in 2004  according to numbers released by japan s finance ministry on wednesday.  china accounted for 20.1% of japan s trade in 2004  compared with 18.6% for the us. in 2003  the us was ahead with 20.5% and china came second with 19.2%. the change highlights china s growing importance as an economic powerhouse. in 2004  japan s imports from and exports to china (and hong kong) added up to 22 201bn yen ($214.6bn;£114.5bn). this is the highest figure for japanese trade with china since records began in 1947. it compares with 20 479.5bn yen in trade with the us.  trade with the us during 2004 was hurt by one-off factors  including a 13-month ban on us beef imports following the discovery of a cow infected with mad cow disease (bse) in the us. however  economists predict china will become an even more important japanese trading partner in the coming years. on tuesday  figures showed china s economy grew by 9.5% in 2004 and experts say the overall growth picture remains strong. analysts see two spurs to future growth as being china s membership of the world trade organisation and lower trade tariffs. during 2004  japan s trade surplus grew 17.9% to 12.011 trillion yen  with more than half the surplus  6.962 trillion yen  accounted for by its trade with the us. in december  the surplus grew 1.8% on a year ago to 1.14 trillion yen thanks to stronger-than-expected exports.