gen x1_x2 = x1*x2                             

gen x1_iv1 = x1*iv2                           

ivreg2 y (x1_x2 x2=x1_iv1 iv1)

其中，x1指标为1-10

回归显示：

Equation not identified; must have at least as many instruments not in the regression as there are instrumented variables

请问问题出在哪里？非常感谢