This is the Emma Maersk. It's how Wal-Mart gets its stuff from China to the U.S. This ship is 207' wide and carries 15,000 containers at 31 knots. Because it's so wide, it doesn't fit in the Panama Canal, so it's strictly a trans-Pacific ship.
These 15,000 containers get shipped back to China EMPTY! Ponder that.
Here's something else to consider. The dollar is ultimately redeemable only in the U.S.A., so the Chinese can only redeem their dollars by buying something in America. If you were Chinese and holding a big bunch of Federal Reserve Notes, what would you buy?