SVAR with long run restrictions

Questions and discussions on Vector Autoregressions
pfb382
Posts: 22
Joined: Fri Apr 14, 2017 5:25 pm

SVAR with long run restrictions

Unread post by pfb382 »

Hi,

I want to run a VAR model with long run restrictions (4 endo variables and 2 exog.). Ideally shock3 has a positive effect on var1 and shock4 has a positive effect on var4.
But it only lets me run the model when I put 4 sign restrictions. Why is that? See code and data attached.

If I dont want sign restriction at all, what do I need to delete? The instructions in the User Manual seem to add more complicated things, which I dont really understand/see the reason for.

Thanks
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kenbur.RPF
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TomDoan
Posts: 7814
Joined: Wed Nov 01, 2006 4:36 pm

Re: SVAR with long run restrictions

Unread post by TomDoan »

If you don't want to put a restriction on a particular column, use a 1 in place of the %sign(...)

compute FLongShort=%dmult(f,$
||%sign(f(1,3)),%sign(f(2,4)),%sign(f(2,3)),%sign(f(4,4))||)

If you don't want to pick signs at all, just do compute FLongShort=f. However, that's not a good idea---there is nothing in the calculation of long run restriction factors that fixes the sign, so you can end up with a bimodal distribution of responses with opposite signs.

By the way, a model long-run restrictions only and with just the upper triangular pattern can be doing using %BQFACTOR (rather than requiring @ShortAndLong), just like the two-variable BQ model. That's the one type of LR restriction model that can be done by a straightforward matrix calculation rather than by iteration.
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