A “speculative bubble,” I wrote then, is “a situation in which news of price increases spurs investor enthusiasm, which spreads by psychological contagion from person to person, in the process amplifying stories that might justify the price increase.” This attracts “a larger and larger class of investors, who, despite doubts about the real value of the investment, are drawn to it partly through envy of others’ successes and partly through a gambler’s excitement.”
在我的书《非理性繁荣》（Irrational Exuberance）第二版中，我尝试给泡沫下一个更好的定义。“投机泡沫”我写道，是“这样一种情况：关于价格上涨的新闻刺激了投资者热情，投资者热情通过心理感染传播，并在此过程中放大可以证明价格上涨合理性的故事。”这吸引了“越来越庞大的投资者群体，他们尽管怀疑投资的真实价值，但也被吸引入局，部分是因为他们嫉妒他人的成功，部分是因为赌徒的兴奋。”