I have mine at 37% 0.o Then again I'm building like 500+ Res. to keep my pop from going into red. But I'm getting 100k+ every turn and I'm building at least 700+ farms to keep up, well then again ima farmer, so if you were to raise tax rate you'd still have to build 100+ Res. To keep pop up then 80-120+ to keep production up too. Then that all changes depending on your country and strat. But you get my point... I hope.