Oil and gas extraction makes up a larger share of national GDP than the country's finance and insurance sectors combined, according to new data released Tuesday by Statistics Canada — but a Calgary economist cautions the numbers come with an asterisk.

The data show Canada's economy surged ahead in May, outpacing analysts' expectations, with growth in oil and gas largely responsible for the upswing.

They also show that oil and gas extraction, alone, now accounts for more than seven per cent of Canada's total GDP, by industry. (And that's not even including support activities for oil and gas, or mining or quarrying, which are sometimes lumped in along with it in the economic data.)

This marks the highest proportion of economic output from oil and gas since 1998, by this particular measure of GDP.

But there's a bit of a catch to these monthly numbers, says University of Calgary economist Trevor Tombe.

Chained 2007 dollars

Statistics Canada reports the data in "chained 2007 dollars," he said, which is a method of calculating the value of each industry's contribution to the economy that nets out the effect of any price changes from one month to the next.

To make those calculations, he said, Statistics Canada assigns each industry its own price index and, since each index is constructed separately from the others, they typically don't add up exactly to the total, real GDP for the current economy.

"Think of today's data as: If prices were the same as they were in 2007, what would each sector's share of GDP be?" Tombe said.

That especially relevant, he added, given the large swings in oil and gas prices over the years.

But, given those caveats, this is how the monthly measure of GDP looks for oil and gas extraction, alongside two other industries that have been historically comparable in terms of their share of economic activity — construction, and finance and insurance.

As you can see in the above chart, Canada's finance and insurance industries slipped just below seven per cent of GDP in May, by this measure. Oil and gas extraction rose slightly above that mark, and is now closing in on construction.

Arlene Kish, director of economics with IHS Markit, said the recent performance of oil and gas has been "impressive" but cautioned that the sector is notoriously volatile and prone to short-term swings.

"Maintenance shutdowns and re-starts heavily impact output data," she said in an email.

"However, it is good to note, though, that non-conventional oil extraction [from the oilsands] hit an all-time high in May, and conventional oil extraction is climbing back up to the highs from 2007. So, the one basic conclusion is that demand for Canadian oil is strong."

The GDP shares for construction and finance remain "pretty stable," she added, "despite the slowing in the housing market and higher borrowing rates, highlighting the resiliency of these two industries."

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