Final answer:
The U.S. federal individual income tax system is characterized as a progressive tax structure, where higher income earners are taxed at higher rates.
Step-by-step explanation:
The federal individual income tax system in the United States uses a progressive tax structure. This means that the tax rate increases as a taxpayer's income increases. For example, someone earning between $50,000 and $80,000 might be taxed at a rate of 20%, whereas someone earning between $300,000 and $1,000,000 might have their income taxed at a higher rate of 35%. This system is designed so that those with higher incomes pay a larger share of their income in taxes compared to those with lower incomes.