Marco Polo, the famous thirteenth-century Venetian merchant, was one of the first Europeans to trade with China. Now imagine that, after a while, the Venetian state became concerned that Polo was purchasing too many silks and spices from China to sell at a profit in Europe. The “trade deficit” he was creating, the authorities worry, would deplete the stock of gold in Venice, while creating jobs for Chinese, rather than for Venetians.