We Don’t Know How Big The UK Illicit Cannabis Market Is But We Know It Is Vast | Scarlett Furlong

Despite cannabis being the most used illicit drug in the UK, little is known about the true scale of the UK cannabis market.

The Crime Survey for England and Wales estimates that 2.2 million people aged 16 to 59 used cannabis in the last year. An unpublished report conducted by the Treasury in 2015 revealed that this amounted to approximately 216 tonnes being consumed. The average street-level price of a gram of cannabis is £10, as reported by the Global Drug Survey. Based on these estimates, UK cannabis consumers are therefore spending over £2bn on black market cannabis per annum. However, the estimated scale of the UK illicit cannabis market generated by previous research should be interpreted with caution as this is likely to be a highly underestimated figure. To achieve a more accurate size of the UK illicit cannabis market, new methods of data collection and analysis should be explored.

The most common method used to calculate the size of the illicit cannabis market is the demand-side approach. This involves multiplying the prevalence figures (obtained by the CSEW) by the estimated amount of cannabis used per year (this is calculated by combining the information on the number of days cannabis is typically consumed by users and the amount of cannabis consumed per day) to give the total consumption. This total consumption is then multiplied by the price – which is worked out by using law enforcement sources and varies depending on potency – to give the market value. 


Several problems arise when relying on general population surveys, like the Crime Survey for England and Wales, to estimate drug prevalence and consumption figures. Heavily marginalised groups are underrepresented. These include those in unstable housing, the homeless and the prison population. It also fails to include young people under 16 and students living in university halls who report high levels of drug use. People being surveyed are also unlikely to be forthcoming about drug use as it is illegal, and they may fear repercussions from exposing their criminal activity. The heterogeneity of drug use is likely to cause an underestimate of cannabis consumed as it is hard to determine drug demand and behaviour. Ultimately, the size of the cannabis market is likely to be heavily underestimated and problematic to calculate.

Some studies seek to calculate the market size by using input data from official drug seizures from the police and UK Border Force. However, this data is more of a metric of police focus rather than size of the market. A recent study by UCL has suggested exploiting data from licit markets to provide insights for the measurement of illicit activities. This can be achieved by using the sales data from rolling papers and roll your own tobacco to attempt to calculate the UK cannabis market. They estimate the UK cannabis market at £3 billion. However, cannabis content of joints is likely to vary on potency and preference and some consumers may prefer to eat their cannabis rather than smoke it, so there are also problems with this approach that arise from over generalisation. 


A study conducted by researchers at the University of Essex utilised data from the Arrestee Survey and Offending Crime and Justice Survey to avoid the under-recording of cannabis consumption which is produced by relying on the CSEW (however, it must be noted that these surveys were abandoned in 2006 and no follow up studies have been conducted). Additionally, they use data from the school survey “Smoking, Drinking and Drugs Use among Young People in England” to bridge the gap in knowledge regarding young people’s drug use. They predict the market size at £1.38 billion in 2010. However, they use the price of cannabis at £6.40 per gram to calculate this estimate so it is likely that the market would be a significant amount larger now if the price of cannabis is £10 per gram.

The UK cannabis market is likely to be massively underestimated, for all the reasons cited in this article. Data collection could be improved in various ways. Surveys among cannabis using populations could aid in obtaining information about the amounts of cannabis users are consuming on average to gain a better estimate. Although it is still likely to be inaccurate as drug demand behaviour is extremely difficult to calculate. The Global Drug Survey has provided a new source of data on cannabis users in the past few years. For example, in their 2017 survey they state that 10.3% of UK cannabis users smoke a joint within 5 minutes to an hour of waking. This data could give better indication on consumption of cannabis users. More data should be collected on those groups who are left out of general population surveys. The UK Focal point report in 2016 stated that cannabis was the most prevalent drug both outside and inside prison, with around 40 to 50 per cent of prisoners reporting use prior to imprisonment and around 10 to 15 per cent reporting use inside prison, thus data on prisoner’s consumption of cannabis would likely affect the market size estimation. New sources of data collection are vital to gain a fuller picture of the current UK cannabis market. Renewed surveys of the Arrestee Survey and Offending Crime and Justice Survey could help to update information conducted by the University of Essex, combined with the new price of £10 per gram of cannabis.

As cannabis policy reform continues to take prominence in various states across the world - notably Uruguay, the United States and Canada – there is no doubt the debate surrounding cannabis will continue to develop in the UK. More research will be warranted into the size of the UK cannabis market and how much money a legally regulated cannabis market could generate. The only way to measure the cannabis market effectively would be by legally regulating the market.

Scarlett Furlong is a Criminal Justice Policy masters student at the London School of Economics. She tweets @scarlettfurlong.