Code:
 +----------------------------------------------------+
  |           id   year     country   sales   countr~s |
  |----------------------------------------------------|
  | PS2011111775   2017   Palestine       2       3023 |
  | PS4001111948   2017   Palestine      45       3023 |
  +----------------------------------------------------+
I am trying to find out how many firms(large; based on sales) are required to represent 50% of country_sales by year and country.
Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input str40 id double year str33 country float(sales country_sales)
"PS2011111775" 2017 "Palestine"    2 3023
"PS4001111948" 2017 "Palestine"   45 3023
"PS5002111951" 2017 "Palestine"  848 3023
"PS4004111952" 2017 "Palestine"   71 3023
"PS2003111643" 2017 "Palestine"   11 3023
"PS2002111909" 2017 "Palestine"   13 3023
"PS2004111535" 2017 "Palestine"   72 3023
"PS3002112921" 2017 "Palestine"   40 3023
"PS1003112957" 2017 "Palestine"  132 3023
"PS3007112108" 2017 "Palestine"   13 3023
"PS5011111455" 2017 "Palestine"   16 3023
"PS2016112695" 2017 "Palestine"   59 3023
"PS2007111979" 2017 "Palestine"   50 3023
"PS1002112958" 2017 "Palestine"  145 3023
"PS1006112053" 2017 "Palestine"  138 3023
"PS5006112997" 2017 "Palestine"   78 3023
"PS2015112738" 2017 "Palestine"  100 3023
"PS5010112959" 2017 "Palestine"   13 3023
"PS1004112600" 2017 "Palestine"  530 3023
"PS5008111955" 2017 "Palestine"    7 3023
"PS2013111914" 2017 "Palestine"    6 3023
"PS5012112072" 2017 "Palestine"  268 3023
"PS3008112065" 2017 "Palestine"   31 3023
"PS4009111049" 2017 "Palestine"    5 3023
"PS1001112942" 2017 "Palestine"   87 3023
"PS4008112055" 2017 "Palestine"   22 3023
"PS1007112953" 2017 "Palestine"  148 3023
"PS3005112951" 2017 "Palestine"   45 3023
"PS3003112946" 2017 "Palestine"   10 3023
"PS3006112943" 2017 "Palestine"   18 3023
"SI0031102690" 2017 "Slovenia"    19 6195
"SI0031102153" 2017 "Slovenia"   861 6195
"SI0031100843" 2017 "Slovenia"    13 6195
"SI0031100637" 2017 "Slovenia"    22 6195
"SI0031104076" 2017 "Slovenia"   149 6195
"SI0031102120" 2017 "Slovenia"  2213 6195
"SI0031107079" 2017 "Slovenia"     1 6195
"SI0021111396" 2017 "Slovenia"     1 6195
"SI0031108994" 2017 "Slovenia"    58 6195
"SI0031100090" 2017 "Slovenia"    40 6195
"SI0031110164" 2017 "Slovenia"    15 6195
"SI0021110513" 2017 "Slovenia"   294 6195
"SI0031101346" 2017 "Slovenia"   510 6195
"SI0031100082" 2017 "Slovenia"   146 6195
"SI0021111313" 2017 "Slovenia"     1 6195
"SI0031105396" 2017 "Slovenia"     2 6195
"SI0031101304" 2017 "Slovenia"    27 6195
"SI0031104290" 2017 "Slovenia"   646 6195
"SI0031103805" 2017 "Slovenia"   211 6195
"SI0031110453" 2017 "Slovenia"    61 6195
"SI0031101296" 2017 "Slovenia"     8 6195
"SI0021111651" 2017 "Slovenia"   787 6195
"SI0021113111" 2017 "Slovenia"     3 6195
"SI0031108200" 2017 "Slovenia"    18 6195
"SI0031110461" 2017 "Slovenia"    23 6195
"SI0031107459" 2017 "Slovenia"     2 6195
"SI0031108655" 2017 "Slovenia"    36 6195
"SI0021113855" 2017 "Slovenia"     2 6195
"SI0031103706" 2017 "Slovenia"    26 6195
"PS3005112951" 2018 "Palestine"   56 2901
"PS2002111909" 2018 "Palestine"   14 2901
"PS4004111952" 2018 "Palestine"   65 2901
"PS1004112600" 2018 "Palestine"  464 2901
"PS1006112053" 2018 "Palestine"  127 2901
"PS3007112108" 2018 "Palestine"   17 2901
"PS3003112946" 2018 "Palestine"   16 2901
"PS5011111455" 2018 "Palestine"   16 2901
"PS2003111643" 2018 "Palestine"   12 2901
"PS3008112065" 2018 "Palestine"   21 2901
"PS3006112943" 2018 "Palestine"   28 2901
"PS1002112958" 2018 "Palestine"  157 2901
"PS5010112959" 2018 "Palestine"   14 2901
"PS2007111979" 2018 "Palestine"   49 2901
"PS2013111914" 2018 "Palestine"    8 2901
"PS2015112738" 2018 "Palestine"   98 2901
"PS3002112921" 2018 "Palestine"   58 2901
"PS2004111535" 2018 "Palestine"   79 2901
"PS5006112997" 2018 "Palestine"   82 2901
"PS2011111775" 2018 "Palestine"    2 2901
"PS5008111955" 2018 "Palestine"    7 2901
"PS4009111049" 2018 "Palestine"    8 2901
"PS1007112953" 2018 "Palestine"  137 2901
"PS5012112072" 2018 "Palestine"  240 2901
"PS5002111951" 2018 "Palestine"  801 2901
"PS4008112055" 2018 "Palestine"   19 2901
"PS1003112957" 2018 "Palestine"  118 2901
"PS1001112942" 2018 "Palestine"   91 2901
"PS4001111948" 2018 "Palestine"   39 2901
"PS2016112695" 2018 "Palestine"   58 2901
"SI0031100090" 2018 "Slovenia"    50 1778
"SI0031103706" 2018 "Slovenia"    27 1778
"SI0031105396" 2018 "Slovenia"     2 1778
"SI0031110461" 2018 "Slovenia"   141 1778
"SI0031104290" 2018 "Slovenia"   440 1778
"SI0031107079" 2018 "Slovenia"     1 1778
"SI0021110513" 2018 "Slovenia"   272 1778
"SI0031108655" 2018 "Slovenia"    44 1778
"SI0031102153" 2018 "Slovenia"   731 1778
"SI0031108994" 2018 "Slovenia"    51 1778
"SI0031102690" 2018 "Slovenia"    19 1778
end