12. 1 Basic Principles of Building Macroeconomic Model o Basic principles of building macroeconomic model &s Researches indicate that many macroeconomic variables, including GDP, all have obvious features of time series Meanwhile, the latest researches also demonstrate macroeconomic variables have another important feature, i. e. random walk 友学经济学院12.1 Basic Principles of Building Macroeconomic Model  Basic principles of building macroeconomic model ❖ Researches indicate that many macroeconomic variables, including GDP, all have obvious features of time series. ❖ Meanwhile ，the latest researches also demonstrate macroeconomic variables have another important feature, i.e. random walk