Hi there, I have a puzzling question that annoys me much and I wonder if you could help.

In my dynare code, if I write the mod file in LEVEL, with a relatively large shock, some of my variables simulated are negative. This negative value is not wished. So I want to avoid this.

One way is to decrease the shock volatility.

However, if the shock volatility remains as before, but I write my mod file in terms of EXP (i.e do log-transformation), then is it by construction my variables are positive?? This is my Q1. Am I allowed to do this and I can really get what i want (non-negative variable values in simulation)?

Q2:

If not, what is the difference between this LEVEL form and log form in dynare simulation?

Q3:

If so, is this a way to impose non-negative constraint in my dynare mod file?

Thanks.

Best,

R