ADF TEST- drift, trend and constant

[Micheal Wembley]

Hi everyone,

I am a beginner when it comes to STATA, and I currently carrying out a time-series analysis using the VECM.

I have a question related to the ADF TEST.

I don't actually know in which situations I should include the drift, the trend and the constant.

Can someone please help me with that?
Thanks in advance

[George Ford]

Depends on the data.

Do all of them (often you'll get to the same conclusion). The trend/constant model is the most general.