How to estimate Them??? strument variable method instrument variable Z=1=a+a1X1+…+a,X (对Ⅻ的滞后项的回归,s值适当选取) The equations to be estimated become Y=Bo+BX,+B2Z,+V cov(Lt, v)=0◼ How to Estimate Them??? Instrument variable method Instrument variable: (Y对X的滞后项的回归，s值适当选取) The equations to be estimated become 1 0 1 1 ˆ ˆ ˆ ˆ Z Y a a X a X t t t s t s = = + + + − − − Y X Z t t t t = + + +     0 1 2 cov( , ) 0 Zt t  =