Canadians consumed nearly 700 tonnes of cannabis in 2015, with a total value ranging somewhere between $5 billion and $6.2 billion, according to rough estimates compiled by Statistics Canada.

The estimates were drafted to add cannabis data to the nation’s statistical system ahead of the federal government legalizing recreational consumption of marijuana.

It said this would make the cannabis market “roughly one-half to two-thirds of the size of the $9.2 billion beer market,” and between 70 to 90 per cent of Canada’s $7 billion wine market.

The agency suggests there were some 4.9 million legal (medical) and illicit cannabis users older than age 15 in Canada that year.

The study suggests Canadians consumed some 697 tonnes of cannabis, costing somewhere between $7 and $9 a gram.

The Liberal government plans on legalizing cannabis by July, 2018.

“In preparation for these changes, it is necessary to adjust Canada’s national statistical system to measure the economic and social impacts of legalized cannabis,” the report summary stated.

Finance Minister Bill Morneau has said that Canada could generate “up to $400 million a year for the first couple of years” off cannabis excise taxes alone.

But politicians have been cautious about throwing around numbers because the market volume is notoriously difficult to estimate. As MP Bill Blair put it recently, criminals “don’t share a lot of data on their market.” A number of government reports tasked with drafting up estimates of the size of the cannabis market in Canada have even relied on self-reporting websites, such as priceofweed.com.

StatsCan’s numbers aren’t totally solid, either. The “experimental” estimates relied on survey data taken from multiple sources.

“Estimating the volume of cannabis consumption is fraught with methodological difficulties, missing information, differing quality instrumental variables and assumptions,” the report said.

“Consequently, there is considerable uncertainty about the level of consumption.”