联立方程组模型，共三个方程，程序如下：

sureg (v23 =v5 v8 v10 v11 v12 v15 v17) (v5=v4 v6 v8 v10 v11 v15 v23) (v8= v3 v6 v7 v17 v23 v5 v16 v22 v18  v19 v20)

结果：
insufficient observations


求高手指点！！

附上错误说明：
insufficient observations：


[P]     error . . . . . . . . . . . . . . . . . . . . . . . . Return code 2001
        insufficient observations;
        You have requested some statistical calculation, and while there
        are some observations, the number is not sufficient to carry out
        your request.
(end of search)