# Trend variables

**URL:** <https://forum.dynare.org/t/trend-variables/5307>\
**Category:** Dynare help (legacy posts)\
**Created:** [1 March 2016 23:37 UTC](https://forum.dynare.org/t/trend-variables/5307 "2016-03-01T23:37:33Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![matheus\_silva92](https://forum.dynare.org/letter_avatar_proxy/v4/letter/m/958977/32.png) [@matheus\_silva92](https://forum.dynare.org/u/matheus_silva92)\
**Post date:** [1 March 2016 23:37 UTC](https://forum.dynare.org/t/trend-variables/5307/1 "2016-03-01T23:37:33Z")

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Hi,

I’m working on a monetary model with technological and populational growth. Therefore, I should have 3 trend variables: technology growing at rate (1+gt), population at rate (1+gn) and money at rate (1+gm).

I’d like dynare to recognize that (1+gm) = (1+gn)\*(1+gt) in the long run, but in the short run they may differ (so my price level changes).

For example, what I’m trying to do is:

trend\_var(growth\_factor= 1+gx) X; //technological progress  
trend\_var(growth\_factor= 1+gn) N; //population  
trend\_var(growth\_factor= 1+gm) M; //money supply

However, I keep getting the error message that my trends are not compatible.

So… Is it even possible to do this in Dynare? I know it’s possible to detrend the variables, but it would be extremely convenient if I could do it this way.

Thanks in advance,  
Matheus

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**Author:** ![jpfeifer](https://forum.dynare.org/user_avatar/forum.dynare.org/jpfeifer/32/5044_2.png) [@jpfeifer](https://forum.dynare.org/u/jpfeifer)\
**Post date:** [2 March 2016 10:52 UTC](https://forum.dynare.org/t/trend-variables/5307/2 "2016-03-02T10:52:11Z")

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That should be possible if all variables are cointegrated. An example is at [github.com/DynareTeam/dynare/blob/master/examples/fs2000\_nonstationary.mod](https://github.com/DynareTeam/dynare/blob/master/examples/fs2000_nonstationary.mod)  
Did you provide growth factors for all variables?

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**Author:** ![matheus\_silva92](https://forum.dynare.org/letter_avatar_proxy/v4/letter/m/958977/32.png) [@matheus\_silva92](https://forum.dynare.org/u/matheus_silva92)\
**Post date:** [2 March 2016 16:25 UTC](https://forum.dynare.org/t/trend-variables/5307/3 "2016-03-02T16:25:18Z")

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Hi Johannes,

Thanks for your response. Do you mind if I upload my code so that you can take a look at it?

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**Author:** ![jpfeifer](https://forum.dynare.org/user_avatar/forum.dynare.org/jpfeifer/32/5044_2.png) [@jpfeifer](https://forum.dynare.org/u/jpfeifer)\
**Post date:** [4 March 2016 14:38 UTC](https://forum.dynare.org/t/trend-variables/5307/4 "2016-03-04T14:38:51Z")

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I can have a look, but cannot promise anything.