帮我看看下面的这个命令有问题吗？为什么运行就有错误啊？提示“Equation not identified. Regessors outnumber instruments.”“no parameters in equation 1”
xtabond2 lnpatent L(1/2).lnpatent L(0/1).lncharge L(0/2).(lnascale lnedu) year1-year9,
gmm(L.lnpatent) iv(L(0/1).lncharge l(0/2).(lnascale lnedu) year1-year9)
nomata noleveleq small