This article is part of a year-long Globe project about Fort McMurray, Alta., which has come to be the emblem of Canada's energy sector, and all the issues that surround it.
The federal census of 2011 records the population of Wood Buffalo, the sprawling municipality that includes Fort McMurray, as roughly 65,000 people. But the municipal census, conducted a year later, pegs the local urban population at about 73,000, and when you include what's called the "shadow population" it's about 116,000, a massive difference.
So what's the real population of Wood Buffalo?
"That's a very a good and a very big question," said Francisco Bermejo, a supervisor in the socio-economic unit at the municipality and one of the people responsible for getting the number right.
Starting next week, the people of Wood Buffalo will be bombarded with messages encouraging them to take part in the 2015 municipal census, which will run to the end of June. This year's slogan is "The count is on." Municipal officials, mindful of the bottom line, will hope that the result shows a population that's still growing despite an oil-price collapse that threatens thousands of jobs in the Alberta region.
For governments, counting people is crucial to how money gets allocated. But there are very few, if any, places in Canada comparable to Wood Buffalo, where the population can nearly double depending on how it's tallied. At the centre of the discrepancy in the various numbers is the question of the shadow population.
Alberta is unusual among provinces because it allows municipalities to conduct their own censuses instead of relying solely on Statistics Canada's mandatory short-form census, which is done every five years.
That's a boon for a place such as Wood Buffalo, where they've been having a census bonanza since the oil sands took off. The municipality conducted nine of its own counts between 2000 and 2012 in addition to the three federal censuses that were done in that time.
Although the phrase shadow population conjures an image of mysterious drifters at the margin of society, it actually refers to just those who may reside elsewhere but work in the municipality for at least 30 days a year. By far, the largest portion of Wood Buffalo's shadow population is made up of the fly-in, fly-out workers who stay in the oil sands work camps north of Fort McMurray.
In 2012, the shadow population count in Wood Buffalo was about 40,000, a staggering number, made up mostly of people living for various periods in the camps. The federal census focuses only on residents, so people who are present in Wood Buffalo on census day and absent from their homes in, say, Newfoundland, are counted as being in Newfoundland.
"If you don't count the shadow population, you'd be missing half of the demographic profile," said Mr. Bermejo.
Wood Buffalo wants the funding it feels it's due for the tens of thousands of people who are in the region and making use of its infrastructure.
Each individual counted is worth between $200 and $225 in population-based grants from the province, Mr. Bermejo said, so encouraging citizens to take part is hugely important. The municipality has budgeted more than $1-million for this year's count and will hire between 100 and 120 enumerators.
"You have to get a high participation rate," Mr. Bermejo said.
The danger for the municipality is that with the stunning speed of the downturn, there will be fewer people around to count this year, as projects are put on hold and workers are sent home.
Dave Odynak, a demographic-research analyst at the University of Alberta, said there's a certain amount of strategy involved in deciding whether to hold a municipal census in a given year. It's hard to beat the quality of a federal census, he said, but it can be worth it to obtain alternate results so long as you're sure that your area is growing.
"If you're losing population, or if your population remained the same, you probably wouldn't do a census," he said.
Mr. Bermejo said their informal estimates suggest significant growth in the number of work camps operating north of Fort McMurray, from about 100 in 2012 to nearly 160 today, he said. He expects the shadow population number will be higher than last time.
Even once they've counted the shadow population in the camps, though, there's also a shadow population in Fort McMurray's urban area, where the municipal census counted roughly 73,000 people, about 12,000 more residents than Statscan found in 2011. The municipality says its own water-use statistics suggest the population is even higher than that, closer to 125,000. Because of the transient nature of the population, it's hard to get a handle on the number of people who are renting rooms and whose landlords are unlikely to reveal these arrangements to enumerators.
"Even if we enumerate every dwelling, we still won't get everybody. The reason is the huge demand on housing here," said Gary Gordon, the municipal census co-ordinator. "There's all kinds of situations where somebody might be renting a couple rooms, and you can get $1,000 a month no problem, but they may not be reporting on their income tax. So they're not going to tell you about all these people."