Department of Finance, University of Luxembourg, Luxembourg, Luxembourg.
PLoS One. 2020 May 12;15(5):e0233024. doi: 10.1371/journal.pone.0233024. eCollection 2020.
I evaluate Alan Greenspan's claim that stock price bubbles build up in periods of euphoria and tend to burst due to increasing fear. Indeed, there is evidence that e.g. during a crisis, triggered by increasing fear, both qualitative and quantitative measures of risk aversion increase substantially. It is argued that fear is a potential mechanism underlying financial decisions and drives the countercyclical risk aversion. Inspired by this evidence, I construct an euphoria/fear index, which is based on an economic model of time varying risk aversion. Based on US industry returns 1959-2014, my findings suggest that (1) Greenspan is correct in that the price run-up initially occurs in periods of euphoria followed by a crash due to increasing fear; (2) on average already roughly a year before an industry is crashing, euphoria is turning into fear, while the market is still bullish; (3) there is no particular euphoria-fear-pattern for price-runs in industries that do not subsequently crash. I interpret the evidence in favor of Greenspan, who was labeled "Mr. Bubble" by the New York Times, and who was accused to be a serial bubble blower.
我评估艾伦·格林斯潘的观点,即股票价格泡沫在乐观情绪高涨的时期积聚,并由于恐惧情绪加剧而倾向于破裂。事实上,有证据表明,例如,在由恐惧情绪加剧引发的危机期间,风险厌恶的定性和定量措施都会大幅增加。有人认为,恐惧是金融决策的潜在机制,并推动了反周期的风险厌恶。受此证据启发,我构建了一个乐观/恐惧指数,该指数基于时变风险厌恶的经济模型。基于美国行业收益 1959-2014 年的数据,我的研究结果表明:(1)格林斯潘是正确的,即价格上涨最初发生在乐观情绪高涨的时期,随后由于恐惧情绪加剧而导致崩溃;(2)平均而言,在一个行业崩溃之前大约一年,乐观情绪就会转变为恐惧情绪,而市场仍然看涨;(3)对于随后没有崩溃的行业的价格上涨,没有特定的乐观/恐惧模式。我对支持格林斯潘的证据进行了解读,格林斯潘曾被《纽约时报》称为“泡沫先生”,并被指责为一连串的泡沫制造者。