何老师讲得是:output gap= actural GDP-potential GDP。
原版书191页写的是:the difference between GDP estimated as if the economy were on its trend growth path and the actual value of GDP。
Early expansion:output gap remains negative,这个和老师讲得一致,但与书上的定义不一致。
2019年用的是output gap=potential GDP - actural GDP
烦请确认。