经济周期专题：什么带动了美国经济的回升？

Group 1: Economic Cycle Characteristics - Since 1948, the U.S. has experienced 12 economic recessions, with notable characteristics observed in the post-World War II economic cycles[18] - Consumer spending is the primary driver for GDP recovery, with consumption growth typically leading or coinciding with GDP growth[22] - Investment growth can lead, lag, or coincide with GDP growth, but historically, it has mostly coincided with GDP recovery in 7 out of 12 recessions[22] Group 2: Investment Dynamics - Residential investment tends to lead the economic cycle, while non-residential and equipment investments usually lag behind[35] - In the last 12 economic downturns, residential investment growth bottoms out before GDP growth in most cases, indicating its leading nature[35] - Non-residential investment growth often lags GDP growth by one to two quarters during economic downturns[35] Group 3: Government Spending - Government spending generally acts as a stabilizer in economic cycles, often leading GDP growth since the 1960s[3] - Prior to 1960, government spending changes lagged behind GDP growth, but post-1960, it has shown a clear leading effect during economic downturns[41] - In the 1989-1991 recession, government spending did not increase significantly despite declining GDP, indicating a unique response to prior fiscal policies[41]