As an industry, it may not yet be as big as oil, but it is older, will last longer, and is vastly more profitable. To profit from oil you have to find it, transport it, refine it and sell it. To profit from psychic readings, you just talk to people and they give you money. And whereas the world will one day run out of oil, it will never run out of people wanting a psychic reading.
Ian Rowland, The Full Facts Book of Cold Reading, 3rd ed., London, 2002, p. 9