Income Tax is not Progressive

The progressive Income Tax is regressive, no matter what anyone tells you. I doesn't tax income, either.

It values labor at exactly zero.

Don't believe it? If you invest $100 and earn $20, you pay taxes on the $20. If, on the other hand, you exchange some of your labor for $120, you pay taxes on all of it. The expense of your time, the sacrifice of working for the benefit of someone else, of not spending that time at leisure or with family, is not deductible. (The Income tax, taxes profit--not principle, as long as it's not in the form of labor--, not income.)

Need more?--if a doctor and an accountant barter services, the IRS will demand that both pay taxes on the value of the service received as though it were income. Neither is allowed to deduct the value of the service that they gave.

Still more?-- The doctor hires an accountant and renders pay in medical care. The doctor gets no tax advantage and the accountant must pay taxes on the services received. But if the doctor pays in money instead, the doctor gets to deduct the expense.

Labor has a value of $0.

As labor is the one resource that nearly all people possess, and often the only one possessed by the poor, and as often the wealthy are able to use other resources, such as education, highly developed skills, or just plain capital, this valuation of labor makes the Income Tax, the most regressive tax that exists.