Differential tax rates on lead-free petrol have encouraged drivers to switch en masse to it.

ECONOMIST: British election briefing: Transport

One obvious example is the quick and relatively painless adoption of unleaded petrol, thanks to differential tax rates which discriminated against leaded petrol.

ECONOMIST: The Liberal Democrats

It's entirely arbitrary to treat differential rates for different levels of income as a structural feature of the tax code but differential rates for different types of income as a tax expenditure.

WSJ: Best of the Web Today: Give Us a Break

The two tax credits in the CBO list--the EITC and the child tax credit--differ from the exclusions, deductions and differential rates in that they are available only to taxpayers with relatively low incomes.

WSJ: Best of the Web Today: Give Us a Break