For the model that primarily uses only CPI data series, we will use a procedure in SAS called the Unobserved Components Model (UCM). While we are calling it a univariate model, we will end up using some components of the CPI time series as independent variables. Remember, we aren't using the nine internal variables that are available to us as part of the business problem. Those nine variables have been used in the multivariate regression model. The components we will be using are the irregular, trend, and seasonal components. We will also leverage some of the plots that can be produced as part of the UCM procedure.
The following is a univariate model code, using Proc UCM:
Proc UCM Data=Model; Id Month Interval=Month; Model ...
