Hi Statlist,
good morning. I am regressing the following variables here represented in a data format:

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input double idfirm int Year float(log_tot_sales recalled_dummy_byfirm inflow_ratio outflow_ratio agefirm) double nprod float(newmolfirm newmolmarket)
1 2004         . .          .          .  .   . . .
1 2005         . .          .          .  .   . . .
1 2006         . .          .          .  .   . . .
1 2007         . .          .          .  .   . . .
1 2008 12.262413 0          .          0  0   4 1 0
1 2009 12.640274 0          0          0  1   4 0 0
1 2010  12.91715 0         .2          0  2   5 1 0
1 2011 13.302264 0   .2857143          0  3   7 1 0
1 2012  13.40613 0  .22222222          0  4   9 1 0
1 2013 13.318162 0   .3571429          0  5  14 1 0
1 2014 13.480266 0   .2631579          0  6  19 1 0
1 2015 13.552082 0          0  .05555556  7  18 0 0
2 2004 16.320004 0          .          0 29   6 1 0
2 2005 16.259003 0          0          0 30   6 0 0
2 2006 16.325436 0          0          0 31   6 0 0
2 2007 16.249718 0          0          0 32   6 0 0
2 2008 16.329601 0  .14285715          0 33   7 1 0
2 2009 16.372135 0          0          0 34   7 0 0
2 2010 16.204067 0          0  .16666667 35   6 0 0
2 2011 16.174494 0          0          0 36   6 0 0
2 2012 16.210453 0          0          0 37   6 0 0
2 2013 16.026436 0          0          0 38   6 0 0
2 2014 15.780373 0          0         .5 39   4 0 0
2 2015 15.507068 0          0          0 40   4 0 0
3 2004 14.717526 0          .          0  9  46 1 1
3 2005  15.29863 1  .19298245          0 10  57 1 1
3 2006 14.427028 0          0 .036363635 11  55 1 1
3 2007  13.07318 0          0  .17021276 12  47 1 0
3 2008 11.988324 0          0  .27027026 13  37 1 1
3 2009 11.322382 0          0  .12121212 14  33 1 0
3 2010  11.74948 0  .23255815          0 15  43 1 1
3 2011 10.473407 0          0   .5925926 16  27 1 1
3 2012  9.682564 0          0      .6875 17  16 1 1
3 2013 10.011105 1  .15789473          0 18  19 1 0
3 2014  9.956585 0          0  .26666668 19  15 0 0
3 2015  10.07903 0          0   .3636364 20  11 1 0
4 2004 15.943534 1          .          0  4 152 1 0
4 2005  15.92585 0  .03797468          0  5 158 1 0
4 2006 16.102678 1   .0867052          0  6 173 1 0
4 2007 16.418432 1  .19907407          0  7 216 1 0
4 2008 16.437866 1  .14624506          0  8 253 1 0
4 2009 16.442644 0  .06985294          0  9 272 1 0
4 2010  16.34378 0 .025089607          0 10 279 1 0
4 2011 16.335884 1 .014134276          0 11 283 1 0
4 2012 16.232006 0  .03082192          0 12 292 1 0
4 2013 16.496168 1  .05501618          0 13 309 1 0
4 2014  17.09195 0  .05504587          0 14 327 1 0
4 2015  17.21494 0          0 .009259259 15 324 1 0
5 2004         . .          .          .  .   . . .
5 2005         . .          .          .  .   . . .
5 2006         . .          .          .  .   . . .
5 2007   3.67482 0          .          0  0   1 1 0
5 2008         . .          .          .  .   . . .
5 2009         . .          .          .  .   . . .
5 2010         . .          .          .  .   . . .
5 2011         . .          .          .  .   . . .
5 2012         . .          .          .  .   . . .
5 2013         . .          .          .  .   . . .
5 2014         . .          .          .  .   . . .
5 2015         . .          .          .  .   . . .
6 2004 17.150093 0          .          0 29   1 1 0
6 2005 15.556746 0          0          0 30   1 0 0
6 2006 13.115322 0          0          0 31   1 0 0
6 2007   9.15078 0          0          0 32   1 0 0
6 2008  5.977219 0          0          0 33   1 0 0
6 2009  7.229989 0          0          0 34   1 0 0
6 2010         . .          .          .  .   . . .
6 2011         . .          .          .  .   . . .
6 2012         . .          .          .  .   . . .
6 2013         . .          .          .  .   . . .
6 2014         . .          .          .  .   . . .
6 2015         . .          .          .  .   . . .
7 2004         . .          .          .  .   . . .
7 2005         . .          .          .  .   . . .
7 2006         . .          .          .  .   . . .
7 2007 10.476154 0          .          0  0   1 1 0
7 2008 10.647244 0          0          0  1   1 0 0
7 2009 12.853146 0          0          0  2   1 0 0
7 2010 13.019257 0          0          0  3   1 0 0
7 2011 12.508344 0          0          0  4   1 0 0
7 2012 12.705505 0          0          0  5   1 0 0
7 2013  12.62807 0          0          0  6   1 0 0
7 2014 12.063735 0          0          0  7   1 0 0
7 2015  10.36172 0          0          0  8   1 0 0
8 2004 21.128635 0          .          0 43 133 1 0
8 2005  21.24772 1          0  .03100775 44 129 0 0
8 2006 21.192095 0          0  .19444445 45 108 0 0
8 2007  21.22827 0          0  .04854369 46 103 1 0
8 2008  21.48543 0          0  .04040404 47  99 1 1
8 2009 21.512186 0          0  .11235955 48  89 0 0
8 2010  21.50318 0          0  .08536585 49  82 0 0
8 2011  21.43127 1 .023809524          0 50  84 1 0
8 2012 21.523424 0  .10638298          0 51  94 1 0
8 2013  21.72658 0  .05050505          0 52  99 1 0
8 2014 21.581614 0          0          0 53  99 1 0
8 2015  21.58638 0          0  .05319149 54  94 1 0
9 2004 23.017605 0          .          0 41  33 1 0
9 2005  23.08483 0          0          0 42  33 0 0
9 2006   23.1325 0          0     .03125 43  32 0 0
9 2007 23.121153 0          0          0 44  32 0 0
end

The command I am using is
Code:
xtreg log_tot_sales recalled_dummy inflow_ratio outflow_ratio agefirm nprod newmolfirm newmolmarket [aweight=cem_weights], fe
and I cannot see the reason why the variables inflow_ratio, newmolfirm and newmolmarket are omitted due to collinearity. They seem to me not constant over idfirm Am I doing something wrong?