Ricardo Caballero and Mohamad Hammour challenged the “cleansing” view of these phenomena. These phenomena affect the lifetime consumption of a representative agent by about one-tenth of a percent, according to Robert Lucas. An empirical “rule” named for Claudia Sahm has historically coincided with these phenomena. The “Great Moderation” saw a reduction in the magnitude and duration of these phenomena, which Christina Romer credited to policy interventions. A Dating Committee within the NBER retrospectively (10[1])declares the start dates of these periods. The early 1980s saw a “double dip” one of these phenomena caused by Paul Volcker’s policies. For 10 points, name this part of the business cycle in which economic activity declines, exemplified by a “Great” one in 2008. ■END■