Hi all,

I have a cross-country panel dataset with multiple countries and firms over the sample period 1981-2019.

I want to drop countries which do not have at least three firms in each financial year. For example, for country A, there should be at least three firms (B,C,D) and all three firms should have data for all the years, from 1981-2019. Otherwise, I need to drop the countries.

Below is a small sample of my data.

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input str32 countryname double(companyid year tot_assets)
"Albania"  3734764 2010   1502902
"Albania"  3734764 2011   1864689
"Albania"  3734764 2012   2337314
"Albania"  3734764 2013   2675742
"Albania"  3734764 2014  10989460
"Albania"  3734764 2015  10776339
"Albania"  3734764 2016  14808676
"Albania"  3734764 2017  13525039
"Albania"  3734764 2018   7653391
"Albania" 12761602 2010  90558535
"Albania" 12761602 2011  93623945
"Albania" 12761602 2012  97485381
"Albania" 12761602 2013 101379321
"Albania" 12761602 2014 101708499
"Albania" 12761602 2015  81461806
"Albania" 12761602 2016  81364754
"Albania" 12761602 2017  77784899
"Albania" 12761602 2018         0
"Albania" 21988056 2010   5117584
"Albania" 21988056 2011   6203623
"Albania" 21988056 2012   6286929
"Albania" 21988056 2013   6203736
"Albania" 21988056 2014   6262487
"Albania" 21988056 2015   6264344
"Albania" 21988056 2016   7531626
"Albania" 21988056 2017   8594377
"Albania" 21988056 2018         0
"Albania" 22866044 2010 277983651
"Albania" 22866044 2011 322854297
"Albania" 22866044 2012 318918623
"Albania" 22866044 2013 291796555
"Albania" 22866044 2014 276446521
"Albania" 22866044 2015 290457704
"Albania" 22866044 2016 270537453
"Albania" 22866044 2017 250454912
"Albania" 22866044 2018         0
"Albania" 26269860 2010  40610102
"Albania" 26269860 2011  39850575
"Albania" 26269860 2012  39979809
"Albania" 26269860 2013  40360109
"Albania" 26269860 2014  36804190
"Albania" 26269860 2015  34967025
"Albania" 26269860 2016  33233585
"Albania" 26269860 2017  34163812
"Albania" 26269860 2018         0
"Albania" 29571446 2010 120632012
"Albania" 29571446 2011 129033450
"Albania" 29571446 2012 129932085
"Albania" 29571446 2013 139237787
"Albania" 29571446 2014 616392174
"Albania" 29571446 2015 600014080
"Albania" 29571446 2016 302304744
"Albania" 29571446 2017 154246155
"Albania" 29571446 2018         0
"Albania" 33957004 2010         0
"Albania" 33957004 2011  56755352
"Albania" 33957004 2012  62098356
"Albania" 33957004 2013  69918648
"Albania" 33957004 2014  71527268
"Albania" 33957004 2015  73277802
"Albania" 33957004 2016  81221920
"Albania" 33957004 2017  81419103
"Albania" 33957004 2018         0
"Albania" 40275950 2010  71020392
"Albania" 40275950 2011  84217207
"Albania" 40275950 2012  91824641
"Albania" 40275950 2013 107467359
"Albania" 40275950 2014 370930389
"Albania" 40275950 2015 572771661
"Albania" 40275950 2016 165483106
"Albania" 40275950 2017 179581853
"Albania" 40275950 2018         0
"Albania" 43833537 2010  21343687
"Albania" 43833537 2011  23415942
"Albania" 43833537 2012  28078859
"Albania" 43833537 2013  32675593
"Albania" 43833537 2014  35824183
"Albania" 43833537 2015  38166191
"Albania" 43833537 2016  41615106
"Albania" 43833537 2017  46538628
"Albania" 43833537 2018         0
"Albania" 44456832 2010   8751527
"Albania" 44456832 2011  13716913
"Albania" 44456832 2012  17381927
"Albania" 44456832 2013  22498656
"Albania" 44456832 2014  26909454
"Albania" 44456832 2015  26087476
"Albania" 44456832 2016  26429322
"Albania" 44456832 2017  28016310
"Albania" 47018265 2010 364948000
"Albania" 47018265 2011 380793000
"Albania" 47018265 2012 390578000
"Albania" 47018265 2013 395942000
"Albania" 47018265 2014 862343000
"Albania" 47018265 2015 494552000
"Albania" 47018265 2016 524656000
"Albania" 47018265 2017 532852000
"Albania" 49209688 2010   7134700
"Albania" 49209688 2011   8673257
"Albania" 49209688 2012   8566644
end
Thank You.