12.1 Basic Principles of Building Macroeconomic model o Dynamic model in macroeconomics .Income-expenditure model C+I c=a+by yt-byt1=1+ 友学经济学院Dynamic model in macroeconomics ❖Income-expenditure model 12.1 Basic Principles of Building Macroeconomic Model yt=ct+It ct=a+byt-1 yt -byt-1 =It+a