Concrete example (no idea if this is how it works for exact figures, just guessing, it's about the concept)
tax 10%
science 80%
luxury 10%
4 gold per turn
tax = 0.4
science = 3.2
luxury 0.4
this would allocate 3 gold to science, and with the one left over gold, would allocate to luxury or tax, as they have the highest remainder. Lets say for the sake of example, it goes to luxury, giving a total of 1 gold to luxury, and 3 to science.
Now move science to 90%, and tax to 0% and you get
tax = 0
science = 3.6
luxury = 0.4
Now luxury would get 3 gold, plus the 1 remaining gold for having the highest fractional part. So all 4 gold would go to science, reducing luxuries by 1.
Thus you can change the level of luxuries by one unit without changing your % allocated towards it.
At least by my understanding of how the calculations would logically work.
