The oil that keeps the economy working smoothly. Economic efficiency is likely to be greatest when information is comprehensive, accurate and cheaply available. Many of the problems facing economies arise from people making decisions without all the information they need. One reason for the failure of the command economy is that government planners were not good at gathering and processing information. Adam Smith’s metaphor of the invisible hand is all about how, in many cases, free markets are much more efficient at processing information on the needs of all the participants in an economy than is the visible, and often dead, hand of state planners. Asymmetric information, when one party to a deal knows more than the other party, can be a serious source of inefficiency and market failure. Uncertainty can also impose large economic costs. The internet, by greatly increasing the availability and lowering the price of information, is helping to boost economic efficiency. But there are inefficiencies the internet will not be able to solve. Uncertainty will remain a huge source of economic inefficiency. Alas, potentially the most useful information, about what will happen in the future, is never available until it is too late.