[justlurking]

and tax revenues historically don’t exceed 18%

It depends on what taxes you include.

This is all taxes: individual and corporate income, social insurance, and excise. Note that the tax rate has hovered just above 20%.

You can find graphs of average tax rate, by the type of tax, at: US Federal Taxes by Income Level. They were derived from data published by the Congressional Budget OFfice -- which is also archived on that page.

[PghBaldy]

Tax rate is not the same as tax revenue.

[achilles2000]

Revenues, not rates.

5% of GDP would be about right if we have a legitimate government.