为什么经济衰退大多发生在共和党的任期内

突然有个有趣的现象浮现出来，就是从1980年开始，为什么经济衰退大多发生在共和党的任期内。这个问题很有意思。

1980 recession	Jan–July 1980
Early 1980s recession	July 1981 – Nov 1982
Early 1990s recession	July 1990 – Mar 1991
Early 2000s recession	March 2001–Nov 2001
Great Recession	Dec 2007 – June 2009[49][50]