Model with Random Walk


I would like to solve the standard RBC model where the technology shock follows a random walk (i.e. unit root).

How do specify the model in Dynare?

So far, I have detrended the model and the detrended shock is just IID over time.
The problem is that the IR look strange. Essential, all endogenous variable react at the time of the shock but there is no persistence.

Can anyone point me to an example? I am not looking for code that does estimation.


Attached is an example, with two unit-root shocks.

example1.mod (670 Bytes)