Find my approach based on 'pivoting' your dataset as reference below and stored in attached workbook version 10.5 located in the original thread.
1. Pivot your dataset first. Pivoting is explained Pivot Data from Columns to Rows - Tableau
2. Drag the required objects to the indicated locations and right click Pivot Field Values > Text menu > Quick Table Calculation > Percent of Total
and Pivot Field Values > Text menu > Compute Using > Cell
Hope it helps,
citizen nalmai v10.5.twbx 120.2 KB
Norbett's answer is the best way to do it by pivotting, which you will be able to do if your data source is excel.
The alternative approach is a bit more manual - You'll have to create a new calculated field for the total by adding up your two fields citizen and permanent resident population.
Then you'll have to find a citizen % by doing sum(cititzen population)/sum(total), and another for the permanent resident %.