What is more difficult for monetary policy is to affect potential growth. That depends very much on the growth of labour supply, technological progress, increasing productivity, organization of production. That’s the supply side. The effects of monetary policy on that are very indirect. Europe has a big problem of low potential  BIS central bankers’ speeches  1  growth.
It starts with demography: the working population is decreasing, so productivity has to be increased even more to compensate for it. Potential growth is very low and in present conditions, we fear that this will be a protracted period of low growth. This prospect of protracted low growth is shared by all advanced economies.