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Last week the parliamentary budget office estimated the GDP impact would be closer to $10 billion, although it didn’t account for what governments might do with the revenues, noting cuts to corporate and personal income taxes could lower that estimate.

Provinces can currently decide how to use the revenues from a carbon price if they implement the system on their own. B.C. cut income taxes to offset the carbon tax cost to individuals, while Alberta cut rebate cheques to low- and middle-income families.

Ottawa will decide how the revenues are spent if it imposes a carbon price on a jurisdiction, and has committed to returning all the proceeds, likely in the form of rebates to families and businesses.

The report notes the numbers are only preliminary because the actual impact will depend on the kind of carbon pricing systems provinces put in place, including what is done with the revenues.

Most economists and environmental experts say carbon pricing will only work if the price rises significantly beyond $50. In British Columbia, emissions initially went down after a carbon tax was introduced there in 2008, but started creeping upwards again after the tax stopped rising in 2012.

McKenna says the four provinces that have a carbon price already are also the four provinces with the strongest economies in Canada.

The report marks the first time Ottawa has provided any real estimate of the impact of its $50-per-tonne carbon price, despite the fact the policy to enforce a national carbon price was unveiled 18 months ago. The Conservatives have pilloried the government for that silence ever since.