T he jargon of economics and finance contains numerous colorful expressions to denote a market-determined asset price at odds with any reasonable economic explanation. Such words as "tulip mania," "bubble," "chain letter," "Ponzi scheme," "panic," "crash," and "financial crisis" immediately evoke images of frenzied and probably irrational speculative activity. Many of these terms have emerged
... [Show full abstract] from specific speculative episodes which have been sufficiently frequent and important that they underpin a strong current belief among economists that key capital markets sometimes generate irrational and inefficient pricing and allocational outcomes. Before economists relegate a speculative event to the inexplicable or bubble category, however, we must exhaust all reasonable economic explanations. While such explanations are often not easily generated due to the inherent complexity of economic phenomena, the business of economists is to find clever fundamental market explanations for events; and our methodology should always require that we search intensively for market fundamental explanations before clutching the "bubble" last resort. Thus, among the "reasonable" or "market fundamental" explanations I would include the perception of an increased probability of large returns. The perception might be triggered by genuine economic good news, by a convincing new economic theory about payoffs or by a fraud launched by insiders acting strategically to trick investors. It might also be triggered by uninformed market participants correctly inferring changes in the distribution of dividends by observing price movements generated by the trading of informed insiders. While some of these perceptions might