↑Shiller, Robert (23 July 2012). "Bubbles without Markets". Project Syndicate. Retrieved 17 August 2012. A speculative bubble is a social epidemic whose contagion is mediated by price movements. News of price increase enriches the early investors, creating word-of-mouth stories about their successes, which stir envy and interest. The excitement then lures more and more people into the market, which causes prices to increase further, attracting yet more people and fueling 'new era' stories, and so on, in successive feedback loops as the bubble grows.