Stock Prices, News, and Economic Fluctuations
提出一种方法检验商业周期是否可分解为需求冲击和技术冲击，发现数据不支持传统分解，而支持主要由一种短期不改变生产率但长期影响生产率的冲击驱动，该冲击约占周期波动的50%，解释为关于未来技术机会的新闻。
A common view in macroeconomics is that business cycles can be meaningfully decomposed into fluctuations driven by demand shocks - which are shocks that have no short- or long-run effects on productivity - and fluctuations driven by unexpected changes in technology. In this Paper we propose a means of evaluating this view and we show that it is strongly at odds with the data. In contrast, we show that the data favours a view of business cycles driven primarily by a shock that does not affect productivity in the short run - therefore it looks like a demand shock - but affects productivity in the long run. The structural interpretation we suggest for this shock is that it represents news about future technological opportunities. We show that this shock explains about 50% of business cycle fluctuations and therefore deserves to be acknowledged and further understood by macroeconomists.