Nothing is so salutary for the Chinese economy as growth in the United States, and nothing is so good for copper and iron ore prices as a strong Chinese economy. The recent drop in the U.S. jobless rate rippled across the world to these metals, and their exchange traded funds gained as a result.

Forty percent of China's GDP comes from exports, so there needs to be demand from across the Pacific.  With more Americans working, there will be more consumer spending in the United States.

That's why Friday's economic news boosted China's blue chip ETF,  the iShares FTSE China 25 Index Fund ( FXI , quote ), which was up 1.38%.

China uses more iron ore than any country for its steel production. That's why a rise in the FXI also triggers an increase in iShares Global Materials ( MXI , quote ), the ETF for iron.   On Friday, the MXI rose 0.92%

Meanwhile, the iPath DJ-UBS Copper Total Return Sub-Index ETN ( JJC , quote ) jumped 3.29%.  China is the world's largest consumer of copper, using 38% of the red metal.  If the American economy is growing, than China is exporting more, increasing the demand for copper.

Hopefully more positive U.S. economic data is on the way. When it is released, traders should go long on FXI, MXI and JJC.