Does it come from the fact that prices are rigid in DSGE models? Or that there is imperfect competition?
The result that monetary policy can affect real variables itself is due to price stickiness, but the price stickiness in labor markets is caused by market imperfections. Furthermore, assumption on imperfect competition in goods market and thus allowing firms to earn markup also has a role as well but in principle you can have DSGE models with just wage stickiness and labor market imperfections and have NK DSGE model. NK DSGE is not a single model it’s a family of models.
Without price rigidity or imperfect competition (that is to say having an RCB model rather than a DSGE model), would it mean that any monetary policy shock (or any demand shock) would only cause inflation?
- In canonical RBC models monetary policy would only change price level. However, there exist some RBC models where the money is non neutral.
- RBC is not opposite of DSGE. DSGE stands for dynamic stochastic general equilibrium model. Both RBC and NK models can be DSGE models. With perfect markets you would have RBC DSGE model. RBC is in fact an example of one of the earliest DSGE models (see Christiano et al 2017).