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Where the plans really differ is in how they would pay for these cuts. Roughly speaking, they would cost about $20 billion, $30 billion and $40 billion respectively, not counting any offsetting increases in revenue from faster economic growth.

Chong would introduce a carbon tax, starting at $10 in 2021 and rising to $100 by 2030. But he’d bring in his income tax cut in year one: the “revenue-neutral” carbon tax is actually revenue-negative throughout the phase-in period.

The top combined rate in Canada’s two largest provinces is now around 54 per cent — among the highest in the OECD.

Bernier is vaguer, saying he would make deep cuts in spending, notably for corporate welfare, and would phase in his income tax cuts only as and when there was fiscal room, after balancing the budget.

Peterson, with the simplest and starkest plan, finances his in the simplest way: by raising the GST four percentage points.

In each case, this would seem to leave them several billion dollars short. So both Chong and Bernier — I have to imagine Peterson would not be averse — propose to eliminate a number of the many special-interest credits and deductions cluttering up the tax system, collectively known as “tax expenditures.” These have become the target for tax reformers as they have proliferated, and with good reason.

As the name implies, tax expenditures are spending programs by another name — only because they are delivered through the tax system do not attract anything like the same scrutiny.

Typically they are addressed to particularly narrow constituencies a government wishes to court. As such, they rarely meet tests of good tax design: either they reward taxpayers for things they would have done anyway, or induce them to do things they would never think of doing on their merits; on top of which they are often of greatest benefit to those least in need.