6-13 Statement of the order condition Statement of the Order condition Let g denote the number of structural equations An equation is just identified if the number of variables excluded from an equation is G-1 If more than g-l are absent it is over-identified If less than g-1 are absent it is not identified Example the ys are endogenous. while the Xs are exogenous Determine whether each equation is over-, under-, or just- identified 1=a+ax1y2+33+a4X1+a5X2+l 12=A6+A13+A2X1+ (14)-(16) ro +ril2+ C Chris brooks2002,陈磊2004© Chris Brooks 2002, 陈磊 2004 6-13 Statement of the Order Condition • Let G denote the number of structural equations. • An equation is just identified if the number of variables excluded from an equation is G-1. • If more than G-1 are absent, it is over-identified. • If less than G-1 are absent, it is not identified. Example • the Y’s are endogenous, while the X’s are exogenous. Determine whether each equation is over-, under-, or just￾identified. (14)-(16) Statement of the order condition Y Y Y X X u Y Y X u Y Y u 1 0 1 2 3 3 4 1 5 2 1 2 0 1 3 2 1 2 3 0 1 2 3 = + + + + + = + + + = + +          