如题，想对数据进行gmm回归。
  一个面板数据，想用因变量之后一期做iv。
代码如下
xtset scode year

xtreg  synch loganal logsize logvol year05 year06 year07 year08 year09 year10 indb indc indd inde indf indg indh indi indj indk indl indm

gmm (synch-{b0}-{b1}*loganal-{b2}*logsize-{b3}*logvol-{b8}*year05-{b9}*year06-{b10}*year07-{b11}*year08-{b12}*year09-{b13}*year10-{b15}*indb-{b16}*indc-{b17}*indd-{b18}*inde-{b19}*indf-{b20}*indg-{b21}*indh-{b22}*indi-{b23}*indj-{b24}*indk-{b25}*indl-{b26}*indm), xtinstruments(logsize logvol year05 year06 year07 year08 year09 year10 indb indc indd inde indf indg indh indi indj indk indl indm, lags(1))   winitial(xt l) wmatrix(hac bar opt)
但是只能得到错误……
warning: 4808 missing values returned for equation 1 at initial values
             gmm_xtZ_i():  3301  subscript invalid
           gmm_ABond_W():     -  function returned error
              _gmm_wrk():     -  function returned error
                 <istmt>:     -  function returned error

如果不管面板的话
reg  synch loganal logsize logvol year05 year06 year07 year08 year09 year10 indb indc indd inde indf indg indh indi indj indk indl indm

gmm (synch-{b0}-{b1}*loganal-{b2}*logsize-{b3}*logvol-{b8}*year05-{b9}*year06-{b10}*year07-{b11}*year08-{b12}*year09-{b13}*year10-{b15}*indb-{b16}*indc-{b17}*indd-{b18}*inde-{b19}*indf-{b20}*indg-{b21}*indh-{b22}*indi-{b23}*indj-{b24}*indk-{b25}*indl-{b26}*indm), instruments(synch logsize logvol year05 year06 year07 year08 year09 year10 indb indc indd inde indf indg indh indi indj indk indl indm)   winitial(identity)

倒是可以得到结果

求助为什么啊~
谢谢