A zero-sum game is one in which the gains of one player are exactly balanced by the losses of another. In India a local NGO has invented a new sort of zero sum which, it hopes, will leave everyone better off: the zero-rupee note. The note is not legal tender. It is simply a piece of paper the colour of a 50-rupee note with a picture of Gandhi on it and a value of nothing. Its aim is to shame corrupt officials into not demanding bribes. And it's working!
