Does economic growth create more or less equality? Do unequal societies grow more or less slowly than equal ones? Economists have debated these questions for as long as anyone can remember. One problem is to agree which sort of inequality matters: equality of outcome (that is, income) or of opportunity? Another is how then to measure it. Equality of opportunity, which, in theory, should make a difference to growth, because it is about giving people the chance to make the most of their human capital, is probably beyond the ability of statisticians to analyze rigorously. The most often used measure of income inequality is the Gini coefficient. The evidence suggests that extreme poverty is more likely to slow growth than income inequality itself. This is because very poor people cannot buy the education they need to enable them to become richer and their children may be forced to forgo schooling in order to work for money. Economic growth has generally reduced inequality within a country. This has been partly as a result of redistributive tax and benefits systems, which have become so significant that they may now be causing slower growth in some countries. The availability of welfare benefits may have discouraged unemployed people from seeking out a better job; and the high taxes needed to pay for the benefits may have discouraged some wealthy people from working as hard as they would have done under a friendlier tax regime. However, the new economy may see inequality in rich countries widen again, thanks to its alleged winner-takes-all distribution of financial rewards.