‘Trade provided the reason for the first interaction between American citizens and Chinese subjects in the late 18th century,’ the State Department's historical office reminds us. Recalling the New York-to-Canton voyage of the optimistically named Empress of China – it ferried over 39 tons of ginseng, and carried back a cargo of porcelain, silk and tea – the Department goes on to remind us that trade ‘accounts for the majority of contacts between citizens of the two nations today’.

Few of us need the reminder. In fact, to many trade is America's contemporary relationship with China.

In 2008, the container ships which are the Empress' great-great-great-grandchildren unloaded 8 million containers of goods at American docks, weighing in at a combined total of 70 million tons and valued at over US$340 billion. They carried a third of Americans' silks, a fifth of our tea and half our porcelain – along with 17 million tons of shrimp, 70 million electronic calculators, 340 million pairs of sunglasses, 50 million kilos of soap, 37 million video players, ­nine-tenths of the toys under American Christmas trees and all the souvenir baseball caps sold by Major League Baseball.

The flow of goods the other way is a good deal smaller: US$80 billion, plus another US$20 billion in services. But even this places China above Japan and Germany as the third-ranking buyer of American farm products, commercial services and factory goods.