By clearly linking a tax to overall spending on the NHS, it can help reconnect voters with the purpose of taxation, but makes healthcare spending vulnerable to macroeconomic shocks and cycles.
George Osborne abolished the top rate of tax after it "only" raised £1bn - but which welfare cuts could have been avoided for that amount?
The Chancellor appears to rule out a 10p tax rate for the Budget and says raising the personal allowance is "a better policy".
Through no effort of their own, landowners reap a £100bn annual windfall. Caroline Lucas's bill shows the way towards a moral capitalism.
The Labour leader's speech has reminded voters of two distinctive and popular Lib Dem policies: increasing the personal allowance and introducing a mansion tax.
Conservative MP Graham Brady demands the abolition of Air Passenger Duty but Robert Halfon tells the New Statesman it would be the wrong move.
The party plans to adjust thresholds elsewhere in the tax system, so that higher-earners don't gain from a lower starting rate of income tax.