- WORLDWIDE VS. TERRITORIAL: Most nations aim to impose taxes on economic activity that takes place within their borders
- INCOME VS. CONSUMPTION: Many economists have argued that taxes should be levied based on consumption rather than income.
- ORIGIN-BASED VS. DESTINATION-BASED TAXATION: The corporate tax system is now origin-based.
- DEBT VS. EQUITY: Now, firms can deduct interest payments to bondholders, but they cannot deduct dividend payments to equity holders.
Mankiw thinks that Congress is moving in the right direction in all four dimensions.