Code:
. xtnbreg collab_weight lie_dummy lmie_dummy umie_dummy hie_dummy crudeoil distance exp_goods imp_goods langcom colotrad t i.year
> if year <1998, pa difficult vce(robust)

Iteration 1: tolerance = .77210018
Iteration 2: tolerance = .44260885
Iteration 3: tolerance = 2.8172375
Iteration 4: tolerance = .99112408
Iteration 5: tolerance = .5789772
Iteration 6: tolerance = .28003152
Iteration 7: tolerance = .86038193
Iteration 8: tolerance = 3.1303517
Iteration 9: tolerance = 59.62716
estimates diverging (missing predictions)
r(430);
Code:
. xtpoisson collab_weight lie_dummy lmie_dummy umie_dummy hie_dummy crudeoil distance exp_goods imp_goods langcom colotrad t i.yea
> r, r

Fitting Poisson model:

Iteration 0:   log pseudolikelihood =   -5819637  (not concave)
Iteration 1:   log pseudolikelihood = -5761440.7  (not concave)
Iteration 2:   log pseudolikelihood = -5549424.1  
Iteration 3:   log pseudolikelihood = -5442723.5  (backed up)
Iteration 4:   log pseudolikelihood = -5430822.3  (backed up)
Iteration 5:   log pseudolikelihood = -4420310.9  (backed up)
Iteration 6:   log pseudolikelihood = -3460335.3  (backed up)
Iteration 7:   log pseudolikelihood = -3036263.1  (backed up)
Iteration 8:   log pseudolikelihood =   -1496255  (backed up)
Iteration 9:   log pseudolikelihood = -1037735.7  
Iteration 10:  log pseudolikelihood = -276698.27  
Iteration 11:  log pseudolikelihood = -167061.51  
Iteration 12:  log pseudolikelihood =  -156156.4  
Iteration 13:  log pseudolikelihood = -155926.92  
Iteration 14:  log pseudolikelihood = -155923.43  
Iteration 15:  log pseudolikelihood = -155923.43  

Fitting full model:

Iteration 0:   log pseudolikelihood = -18572.231  
Iteration 1:   log pseudolikelihood = -12952.323  
Iteration 2:   log pseudolikelihood = -11522.121  
Iteration 3:   log pseudolikelihood = -11507.175  
Iteration 4:   log pseudolikelihood = -11507.031  
Iteration 5:   log pseudolikelihood = -11507.031  

Random-effects Poisson regression               Number of obs     =      6,665
Group variable: target                          Number of groups  =        215

Random effects u_i ~ Gamma                      Obs per group:
                                                              min =         31
                                                              avg =       31.0
                                                              max =         31

                                                Wald chi2(38)     =  310476.06
Log pseudolikelihood  = -11507.031              Prob > chi2       =     0.0000

                                  (Std. Err. adjusted for clustering on target)
-------------------------------------------------------------------------------
              |               Robust
collab_weight |      Coef.   Std. Err.      z    P>|z|     [95% Conf. Interval]
--------------+----------------------------------------------------------------
    lie_dummy |  -2.274201   .7879215    -2.89   0.004    -3.818498    -.729903
   lmie_dummy |  -.4998195   .7303129    -0.68   0.494    -1.931207    .9315676
   umie_dummy |   .3827133   .6633518     0.58   0.564    -.9174324    1.682859
    hie_dummy |   2.815289    1.02745     2.74   0.006     .8015247    4.829054
     crudeoil |   1.35e-11   9.19e-12     1.47   0.143    -4.55e-12    3.15e-11
     distance |  -1.64e-07   4.99e-08    -3.29   0.001    -2.62e-07   -6.65e-08
    exp_goods |   2.02e-11   2.63e-11     0.76   0.444    -3.15e-11    7.18e-11
    imp_goods |  -1.24e-11   7.30e-12    -1.70   0.090    -2.67e-11    1.92e-12
      langcom |   .9399202   .5324221     1.77   0.078    -.1036079    1.983448
     colotrad |   1.697512   .5837964     2.91   0.004     .5532924    2.841732
            t |   -.000233   .0001204    -1.93   0.053     -.000469    3.05e-06
              |
         year |
        1989  |   .2327258   .1653442     1.41   0.159    -.0913429    .5567945
        1990  |   .0103387   .1600504     0.06   0.948    -.3033543    .3240317
        1991  |   .2671711   .1818145     1.47   0.142    -.0891787     .623521
        1992  |    .175082   .1103716     1.59   0.113    -.0412423    .3914064
        1993  |   .6880291   .1898473     3.62   0.000     .3159352    1.060123
        1994  |   .8123215   .1816326     4.47   0.000     .4563282    1.168315
        1995  |   .8296807   .2136778     3.88   0.000     .4108799    1.248481
        1996  |   .8666348   .1835742     4.72   0.000     .5068359    1.226434
        1997  |   1.252203   .2266925     5.52   0.000     .8078938    1.696512
        1998  |   1.755356    .160692    10.92   0.000     1.440406    2.070307
        1999  |   1.779675   .1955139     9.10   0.000     1.396474    2.162875
        2000  |   1.774911   .1871909     9.48   0.000     1.408023    2.141798
        2001  |   1.797513   .1857545     9.68   0.000     1.433441    2.161585
        2002  |    1.93671   .2101448     9.22   0.000     1.524833    2.348586
        2003  |   2.144361   .2271368     9.44   0.000     1.699181    2.589541
        2004  |   2.188524   .2846896     7.69   0.000     1.630542    2.746505
        2005  |   2.091397   .2253226     9.28   0.000     1.649773    2.533022
        2006  |   2.222598   .2610636     8.51   0.000     1.710923    2.734273
        2007  |   2.419143    .253332     9.55   0.000     1.922621    2.915664
        2008  |   2.731458   .2579121    10.59   0.000     2.225959    3.236956
        2009  |   3.038362   .2975614    10.21   0.000     2.455152    3.621571
        2010  |   3.786144   .2716868    13.94   0.000     3.253647     4.31864
        2011  |   4.370649   .2968693    14.72   0.000     3.788796    4.952502
        2012  |   4.660286   .2953141    15.78   0.000     4.081481    5.239091
        2013  |   4.969484   .2750056    18.07   0.000     4.430483    5.508485
        2014  |   5.260252   .2840089    18.52   0.000     4.703605    5.816899
        2015  |   5.484816   .2854457    19.21   0.000     4.925353     6.04428
        2016  |   5.649095   .2794348    20.22   0.000     5.101413    6.196777
        2017  |   5.653836   .3033422    18.64   0.000     5.059296    6.248375
        2018  |   5.758926   .3067073    18.78   0.000     5.157791    6.360062
              |
        _cons |   .1529557   .5510348     0.28   0.781    -.9270528    1.232964
--------------+----------------------------------------------------------------
     /lnalpha |   1.542755   2.034685                     -2.445155    5.530664
--------------+----------------------------------------------------------------
        alpha |   4.677457   9.517151                      .0867127    252.3114
-------------------------------------------------------------------------------
LR test of alpha=0: chibar2(01) = 2.9e+05              Prob >= chibar2 = 0.000

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end of do-file

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