 It is a mundane yet intriguing fact that price signals induce people to respond to information they do not possess: such as the changing cost of drilling, or the discovery of a cheap substitute, or that political unrest has made a key input harder to acquire. Having no inkling of those variables, buyers nevertheless respond to them in a rational way, because they know the one thing they need to know: namely, the price (Hayek 1978a, 4).