點解expansionary monetary policy 解決唔到 natural rate of unemploy

首先要搞清楚NRU包含d乜
i) Frictional unemployment
係指d first time enter to labour force同d voluntarily re-enter to labour force既人
搵緊工時既失業

ii) Structural unemployment
係指行業或地區間既demand or supply轉變，但d工人既skill同location唔可以轉得咁快，所以係location or skill既mismatches

要針對呢兩項既問題，先可以減低NRU
但係expansionary monetary policy只能增加real output
real output增加唔代表d人會搵工快d或者d skill學得快d

同埋NRU其實都唔需要解決
因為佢地係voluntary既
voluntary unemployment可以令resources reallocate去個better position
最後其實係會有social gain
只有involuntary既unemployment先要解決，就係cyclical unemployment
因為呢個係economy recession，output下降所導致
所以expansionary monetary policy可以解決倒