st: clarity on varsoc command

["Michael Ndlovu" <Michael.Ndlovu@resbank.co.za>]

Hi

I am trying to create a time-series model with the optimal lags for each variable. I am using Stata version 12.

My understanding of the "varsoc" command is that it gives you optimal lag choice for a set of variables. So if I have type in the command "varsoc y x z" , I will get the optimal lag choices for a model that looks like: y = cons + b1*ylag + b2* xlag + b3*zlag.

My problem with this though is the assumption of the same lag period for all these variables. How do I get optimal lag choice for each variable such that the optimal amount of lags to y is not necessarily the same as x or z. 

Is it correct for me to isolate each variable and make the other variables exogenous

i.e. varsoc y x, exog(z)
      varsoc y z, exog(x)

I just need clarity on whether I am going about this the right way or whether there is another way of finding what I want.  

Regards
Michael



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