The International Journal of Drug Policy released a research report titled, “Association of recreational cannabis legalization with changes in medical, illegal, and total cannabis expenditures in Canada,” which found that adult use legalization appeared to be displacing the illegal cannabis market.
The report said its data showed that when recreational cannabis laws (RCL) were passed, medical cannabis represented 11.8 % of the market and illegal cannabis 88.2 %. The research determined that at five years post-RCL implementation, medical cannabis decreased to 3.7 %, illegal cannabis decreased to 24.3 %, and licensed cannabis took over 72.0 % of the market.
The report stated,
The overall cannabis market increased in size by 75 % over these 5 years. Illegal cannabis expenditures increased between RCL passage and implementation but decreased immediately post-implementation and had a significant decreasing trend.
The authors did caution that the data could potentially be uncertain when it came to spending for illegal cannabis.

Research method
The researchers said they examined publicly available Canadian national estimates of quarterly household expenditures on medical cannabis, illegal cannabis, and all cannabis product types combined. For the illegal data, cannabis spending was estimated based on several metrics, including the prevalence of use, the frequency of use, and the average amount used per use day. According to the report, the prevalence and frequency of use were estimated based on population-based national surveys. The authors said that the overall size of the cannabis market was first estimated and then illegal expenditures were derived by subtracting medical and licensed sales from the overall estimate.
The study stated that Illegal cannabis prices were gathered from self-reported survey data and crowdsourced data on flower products, while medical and licensed cannabis prices were determined directly from medical producers and retailers for flower and later oil product.s
Conclusion
The report concluded that legalization in Canada appears to be achieving one of its primary goals by displacing the illegal cannabis market. However, the authors also noted that the medical cannabis market has also been affected, meaning less clinical oversight.
“Moreover, the overall cannabis market in Canada has grown substantially in the first five years of legalization, suggesting consumption has increased at the population level,” the report stated. The researchers warned that public health could be impacted by such a big increase in the consumption of legal adult-use cannabis.