input coid year ind size
1 1998 11 100
1 1999 11 120
1 2000 11 113
2 1998 11 201
2 1999 11 220
2 2000 11 230
3 1998 22 330
3 1999 22 221
3 2000 22 234
end
gen ind2=year+ind
bysort ind2: egen i_size=sum(size)
gen rsize=size/i_size*100
format rsize %4.2fc
drop ind2
list

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