宏观经济/商业周期

商业周期

商业周期或经济波动是总经济活动中的起伏。商业周期由两个阶段和两个转折点组成。

1. Two Phases
 
 a. Expansion
  i. Time in which real GDP rises and unemployment declines.
  ii. Sometimes called recovery.
 
 b. Contraction
  i. Time in which real GDP declines and unemployment rises.
  ii. Recession - Six consecutive months of decrease.
   1. A "severe recession" is called a depression.
   2. No official definition of severe (length and depth).

2. Turning points
 
 a. Peak
  i. Real GDP reaches its maximum, stops rising, and begins to decline.
  ii. Determined after the fact.
 
 b. Trough
  i. Real GDP reaches its minimum, stops declining, and begins to rise.
  ii. Determined after the fact.

从一个高峰到下一个高峰，或从一个低谷到下一个低谷的序列是一个商业周期。收缩-低谷-扩张-高峰的模式一遍又一遍地出现，但并不是以规律的、可预测的时间间隔出现。