# CausalImpact: model in the paper and default in the package

I was utilising CausalImpact for a study. Only recently did I realise that the model described in the associated paper was different to the default model implemented in the package.

The paper was read like the default model was Local Linear Trend model for the structural time series. However, the default model used in the package is Local Level Model.

Could the author confirm this?

I think the author should probably make this clear in their online document or in the package help.

The default model in CausalImpact is defined in CausalImpact:::ConstructModel: