用probit 做非平衡面板模型，数据大概有20多万个，但是我加入所有变量可以运算出来，但选择其中几个变量反倒一直出不了结果，一直是下面这个样子。。
. xtprobit EX TFP Hcapital new age

Fitting comparison model:

Iteration 0:   log likelihood = -118985.35  
Iteration 1:   log likelihood = -117693.44  
Iteration 2:   log likelihood = -117691.64  
Iteration 3:   log likelihood = -117691.64  

Fitting full model:

rho =  0.0     log likelihood = -117691.64
rho =  0.1     log likelihood = -110930.81
rho =  0.2     log likelihood = -105581.35
rho =  0.3     log likelihood = -101129.68
rho =  0.4     log likelihood = -97305.565
rho =  0.5     log likelihood = -93949.143
rho =  0.6     log likelihood =  -90964.11
rho =  0.7     log likelihood = -88310.832
rho =  0.8     log likelihood = -85985.556

Iteration 0:   log likelihood = -88292.294  
Iteration 1:   log likelihood = -79372.401  
Iteration 2:   log likelihood = -79284.675  
Iteration 3:   log likelihood = -74893.432  
Iteration 4:   log likelihood = -73035.998  
每次到这里就卡住了，求问大神 是什么原因阿？？