IN 1300 OR so Marco Polo, a Venetian merchant, introduced Europeans to a monetary marvel w
itnessed in China. The emperor, he wrote, “causes the bark of trees, made into something l
ike paper, to pass for money all over his country”.Eventually the West also adopted paper
money, some six centuries after China invented it. More recent foreign travellers to China
have come back agog at the next big step for money: the total disappearance of paper, rep
laced by pixels on phone screens.