Hi,
I require some help with identifying the surviving firms that have survived completely over some sample period. Currently I have an unbalanced panel data from 2005 - 2018. And, I need to identify the surviving firms in my sample that have survived from 2007- 2012. How can I do that? I have provided my sample data as follows. Any help will be greatly appreciated. Thank you.

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input long firmid int Time byte gov_score float(W_LT_ST_Debt W_Cash)
 1 2010 48           0  .15292925
 1 2011 45           0  .14126548
 2 2005 48     .321169  .02889901
 2 2006 48    .4047627 .024768505
 2 2007 57    .4832045  .02869392
 2 2008 57    .4881782 .016597208
 2 2009 57    .5128571 .006899303
 2 2010 57    .5373243   .0772715
 2 2011 57   .45641285   .0647687
 3 2008 54           0   .4868421
 3 2009 43           0   .4462103
 3 2010 52           0   .4036738
 4 2005 57     .056005 .000536697
 4 2006 57  .001273891  .09653819
 4 2008 54           0   .0795885
 4 2009 54           0  .14301102
 4 2010 59   .28258508   .0839134
 4 2011 59   .27573884    .036254
 4 2012 54    .1599355  .05019824
 4 2013 59           0 .025961764
 4 2014 59   .12967676  .08580718
 5 2009 48   .09135466   .2734658
 5 2010 48   .06068646  .22870205
 5 2011 48           0   .1161748
 5 2012 48     .090732   .0860763
 5 2013 48   .05839393  .09071933
 6 2008 52   .07185876 .003424159
 6 2009 52   .05577296 .012392032
 6 2010 57   .05200667 .013328754
 6 2011 57   .05974993  .03943341
 6 2012 54   .06299406  .02925601
 6 2013 57   .05957615 .025026243
 6 2014 48    .0392618  .03067843
 7 2006 52   .28372183  .04316239
 7 2007 52    .3330956 .031383738
 7 2008 52   .24130663 .003161222
 8 2007 52    .4963348   .0989601
 8 2008 52   .49353835  .07482272
 8 2009 52    .4424315  .08442432
 8 2010  .    .4474763  .09543334
 9 2007 55   .25218964  .04434867
 9 2008 55    .3259162  .04957041
10 2014 54    .9057651    .154239
10 2015 57    .9057651   .0909589
10 2016 57    .9057651  .11116965
10 2017 57    .9057651   .0821018
11 2005 63    .1626325 .066101365
11 2006 63   .13441473  .06462578
11 2007 66    .1854028 .069903046
11 2008 71    .2813744  .05571193
11 2009 71   .25422674   .0580557
11 2010 71   .20161726  .09603036
11 2011 71    .1777008  .16195025
11 2012 77    .2228414  .11473773
11 2013 77   .25079745  .10825546
11 2014 71   .28079078  .10222694
11 2015 71    .3454329  .13256301
11 2016 71   .26259747  .12066043
11 2017 66    .2194058  .14295925
11 2018  .    .1718714  .12581424
12 2005 57    .1623847  .15299736
12 2006 57   .10890327  .05375847
12 2007 57   .10358166  .05888252
12 2008 57   .14084162  .04269415
12 2009 57   .15388022  .04240009
12 2010 63        .125 .037144702
12 2011 63    .1593805  .03342482
12 2012 63   .14179687  .03818359
12 2013 68   .11239637  .03489493
12 2014 63    .0921505  .04956073
12 2015 57    .0876798  .06869557
12 2016 63   .07779536  .04878692
12 2017 66   .06846214  .12099922
12 2018  .    .0568215  .09947415
13 2010 57           0   .1369993
13 2011 57           0  .17731404
13 2012 61           0  .12039585
13 2013 61   .05838857  .11612308
13 2014 61   .05496598  .11374457
13 2015 61    .0548386   .1000944
13 2016 61   .03971796   .1269818
13 2017  .   .03942502  .04470734
14 2007 54           0   .1789832
14 2008 54           0  .14229389
14 2009 54           0   .1798879
14 2010 54           0  .13963887
14 2011 54  .000344181  .08589239
14 2012 54  .000249672 .067598775
14 2013 52 .0000287869  .05409062
14 2014 52    .0529207  .06599613
14 2015 52   .05394537 .063130595
14 2016 52   .04610353  .06719059
14 2017 52   .03823113  .05577648
14 2018  .   .06529952   .0553914
15 2007 54   .05873977 .035458125
15 2008 54   .09230971  .03465203
15 2009 54   .08320349 .026454885
15 2010 59   .05037183  .04792475
15 2011 59  .028410075  .07258428
15 2012 61  .020017685  .08544973
end
label values firmid firmid1
label def firmid1 1 "0876711D LN Equity", modify
label def firmid1 2 "1218069D LN Equity", modify
label def firmid1 3 "1334987D LN Equity", modify
label def firmid1 4 "1561649D LN Equity", modify
label def firmid1 5 "1638414D LN Equity", modify
label def firmid1 6 "1655637D LN Equity", modify
label def firmid1 7 "3572335Q LN Equity", modify
label def firmid1 8 "8190169Q LN Equity", modify
label def firmid1 9 "9408593Q LN Equity", modify
label def firmid1 10 "AA/ LN Equity", modify
label def firmid1 11 "AAL LN Equity", modify
label def firmid1 12 "ABF LN Equity", modify
label def firmid1 13 "ACA LN Equity", modify
label def firmid1 14 "ADM LN Equity", modify
label def firmid1 15 "ADN LN Equity", modify