A nation's Income Tax is an uncancellable Policy where a fraction of every working citizen's earnings is given to the government.
Income taxes are progressive; the wealthy pay a bigger fraction than the poor. This improves a nation's Equality and makes a high Income Tax popular among Socialists, but unpopular among the Capitalists, the Middle Income earners, and the Wealthy.
The Income Tax lowers all three kinds of Earnings at different rates; High Earnings are affected twice as much as Low Earnings.
Any income tax rate over 18% will risk encouraging a Black Market.
Any income tax rate over 22% will risk encouraging Tax Evasion.
Middle Income earners won't oppose the income tax until it passes 25%. This is a good rate for a Capitalist nation that still wants to earn some money from the tax.
At 42%, the Income Tax is neither favored or opposed by the Capitalists and Socialists. This is a good rate for a nation that's balancing both capitalism and socialism.
The Wealthy won't begin to oppose the Income Tax until it passes 65%. This is a good rate for a Socialist nation that wants to keep the Wealthy happy.