The INCLUDE= option of the MODEL statement in PROC REG does this.   INCLUDE=4 forces the modeling to use the first 4 variables listed on the right hand side of the equal sing in the MODEL statement. Although, if consumer income s not really a good predictor, I would think you might want to avoid using it, because it could possibly lead to poorer predictions.   Edit: "... because it could possibly lead to lower adjusted R-squared values". In other words, you are probably not improving the model and in some sense adding it in can be harmful. ... View more