A Simple Explanation of Countercyclical Uncertainty
发现劳动力搜索与匹配摩擦会因新匹配流量的非线性导致就业不确定性随求职人数增加而上升，从而产生反周期不确定性。该机制足以解释不确定性与实际活动的动态及其相关性，表明不确定性波动是实际活动的内生反应，不影响经济周期严重程度，也无需政策干预。
This paper documents that labor search and matching frictions generate countercyclical uncertainty because the inherent nonlinearity in the flow of new matches makes employment uncertainty increasing in the number of people searching for work. Quantitatively, this mechanism is strong enough to explain uncertainty and real activity dynamics, including their correlation. Through this lens, uncertainty fluctuations are endogenous responses to changes in real activity that neither affect the severity of business cycles nor warrant policy intervention, in contrast with leading theories of the interaction between uncertainty and real activity dynamics.