Question

a person’s tax obligation divided by his income is called his
marginal social tax rate
marginal private tax rate
margin tax rate
average tax rate

Explanation:

To solve this, we analyze each option:

• "marginal social tax rate" and "marginal private tax rate" relate to the tax rate on an additional unit of income, not the ratio of total tax to income.
• "margin tax rate" is not a standard tax term.
• "average tax rate" is defined as total tax obligation (tax paid) divided by total income, which matches the description in the question.

Answer:

D. average tax rate