League tables are controversial and for good reason. Few things are simple enough to be measured by a single outcome like, for example, the number of exam passes or successful heart operations. But even if we do accept a single yardstick, we haven't yet reckoned with chance, which by itself can produce apparent patterns to delight any tabloid editor.

There are many different types of lottery around the world, but they all share a common aim: to make money. John Haigh explains why lotteries are the way they are.