This could either be done with a flat rule, or by relating the tax
base of a province to its civ level.
tax gold
--------
wilderness 0
civ-1 200
civ-2 250
civ-3 300
civ-4 350
civ-5 400
civ-6 450
(suggest other progressions if you like)
Comments?
-- Rich Skrenta <skrenta@shadow.com>