[HoneyBadger]

You could make a case for the tax rate representing the amount of surplus food that's produced and sold on a land beyond that required to feed the people actually living there.
You could then ask the Devs to arrange the tax percentage scale to give you more supplies-based on the arability of the particular province, and with a high limit-if you lower taxes.
I also think it would be nice (and wise) to represent lower taxes (lower than 100%) increasing growth-again, based on the arability of a particular province.
90%=1% growth
75%=2% growth
50%=3% growth
25%=4% groth
10%=5% growth
0% means that every surrounding province that's being taxed at 100% or more loses 1% of it's growth per month, which migrates to your 0% tax province, *PROVIDING* that you're defending that particular province with a PD of atleast 40, OR have opposing scales from the province the population is migrating from, starting with Order. Example: Order scales migrate to Turmoil, Turmoil migrates to Order. 0 Order moves down the list to heat, growth, luck, etc, until a positive or negative scale attribute is found. No positive or negative scales means no population movement.


It would also be nice if you could have a similar resource-scale that you could lower to increase gold income (representing exported, outgoing trade) or raise, lowering the gold income (representing importation of goods). Either raising or lowering this resource scale should affect growth in a random way, either increasing or decreasing it by a maximum of 10%, to represent moving populations in and out.

Leaving the new resource scale at 100% would represent no trade, and actually reduce unrest over time, since your people would have much less contact with corrupting outside influences. Growth would be unaffected.