The size of the UK illegal drugs economy

CLA research report · Evidence review and estimation
Published: 14 October 2026
Updated: 15 October 2026

Evidence library · How we build our evidence

The main finding

The strongest conclusion is that the familiar £9.4 billion headline is an inadequate description of the present UK drugs economy. It is an estimate for England and Wales in 2016/17, published in the 2020 Black review. More recent official research changes the evidence base substantially, but it does not establish a complete, consistently measured UK total. ^[3]

New Home Office work values supply at £14.3 billion: £12.0 billion for six drugs in England, plus £2.3 billion for cannabis in England and Wales. The September 2026 study labels this year ending March 2024, assuming later wastewater observations represent that period. It leaves the six-drug estimate unextended to Wales because the method is experimental. ^[1]

Our illustrative calculation gives about £17–18 billion a year if spending per resident elsewhere in the UK matches the observed geographies and the other assumptions below hold. This is a conditional scenario for interpreting scale, not a new official estimate, a 2026 forecast, or a statistically established range. A broader stress test runs from approximately £11 billion to £24 billion, without bounding all uncertainty.

We recommend leading public discussion with the verified partial estimate and its coverage. The scenario belongs alongside a transparent calculation. It would be misleading to replace one overconfident headline with another.

1 What the economy means

This paper focuses on annual final consumer expenditure on illegally supplied drugs: the money paid at the retail end of the market. The question is how large that expenditure is, how estimates differ, and which conclusions survive scrutiny. A complete economic account would also distinguish domestic production, imports, exports, intermediaries, profits and associated harms. Existing evidence does not support one reliable number for all of these together.

A simple example shows the double-counting problem. If a supplier sells a quantity to a retailer for £400 and the retailer sells it to consumers for £1,000, final expenditure is £1,000, not £1,400. Summing bank transfers, wholesale deals and retail purchases measures repeated movement of money as well as economic activity. Neither that sum nor the retail total is automatically a measure of profit.

Lawful prescriptions and authorised medical or veterinary supplies are outside the target market. Illegal diversion of medicines is within scope in principle, but is incompletely measured. Alcohol and tobacco are excluded. Personal cultivation and gifts also require care: valuing all consumption at a retail price can produce an equivalent market value that differs from money actually paid. This distinction matters when wastewater measurements are monetised.

2 The principal estimates

Table 1 records original periods and geographies. Amounts are nominal values as reported by their sources, not inflation-adjusted comparisons. Rows overlap and cannot be added or averaged. A later publication date does not necessarily mean newer underlying observations.

Why the historical estimates differ

Pudney and colleagues combined school, household-related and arrestee evidence, then extrapolated from England and Wales to the UK. Their report explains that differences from the earlier study reflect both falling prices and changed methods. It also flags under-reporting that was not fully adjusted in the baseline. The apparent fall between those studies is therefore not a clean measure of market contraction. ^[5]

The 2013 Home Office work estimated expenditure using the Offending, Crime and Justice Survey and Arrestee Survey, with population and arrest adjustments. Its Annex 2 explains differences from earlier work. The 2019 organised-crime publication then used ONS estimates rooted in earlier survey benchmarks and updated for users, prices and purity. These are related estimation families, not independent votes about the true answer. ^{[7, 8]}

The older Black-review total is also frequently recycled. A parliamentary answer in September 2025 directed a question about recent cannabis, cocaine and opioid valuations back to the 2020 evidence pack. Repetition in a current statement does not refresh an estimate’s reference year. ^[15]

The conflict with national accounts

The ONS series records £3.044 billion for 2024 and £2.911 billion for 2025 in its 30 September 2026 release. These are current-price household expenditure figures, not net profits or value added. The release date matters because historical observations can be revised. ^[4]

Its disagreement with the newer consumption-based estimates is too large to hide in a footnote. The appropriate response is a reconciliation of methods, not a midpoint. An average would have no clear geographical scope, drug coverage or statistical interpretation. The ONS series is valuable evidence that official measurements remain inconsistent; its existence does not independently validate the higher model, and the higher model does not by itself prove the ONS series wrong.

The ONS’s 2016 methods article listed further improvements to the sources and methods for narcotic drugs among its future plans. Consistency within an accounting series should not be confused with direct observation of purchases. ^[28]

3 What the new wastewater evidence shows

Update of 15 October 2026

A separate Home Office release published on 14 October 2026 extends the consumption evidence to March 2026. Its trend analysis follows 16 English sites covering around 22% of England’s population, selected for continuity rather than national representativeness. The annual comparisons use seven-day samples within January to April sampling windows, rather than full-year consumption totals. ^[29]

Across those sampled locations, estimated cocaine consumption fell by 7% and ketamine by 11% between the early-2025 and early-2026 windows. These changes do not establish equivalent changes in national spending. The release provides no replacement national monetary estimate. We therefore retain the earlier valuation below and do not apply these percentages to the UK scenario. Its reference periods and conditional status remain unchanged. ^[29]

The earlier valuation

WAND’s national estimates use 42 English sites covering 28% of the population and extrapolate to England. They cover August 2024 to July 2025, apply 2025 NCA retail pricing and purity information, and remain experimental. The report was updated on 8 October 2026. Cocaine includes powder and crack. ^[2]

Source ^[2], Table 1. Reported values are reproduced rather than recalculated from kilograms. Cannabis is excluded. Heroin’s biomarker is particularly unstable; medical use, direct disposal and population movement can also affect measurement. The uncertainty measures do not justify treating the central values as observed receipts.

The intellectual advantage of wastewater is straightforward: a person need not disclose drug use to an interviewer to contribute to the signal. Its difficulty is equally important: a chemical concentration must be converted into consumption, projected beyond sampled catchments, then valued. Each step introduces a different question. Accurate laboratory measurement alone does not establish accurate national revenue.

McCall and colleagues’ review of biomarker stability explains why transformation during sewer transit and sample storage can systematically distort inferred use. This is a methodological reason to compare wastewater with other evidence, not a reason to dismiss it. The direction and magnitude of error depend on the substance and measurement process. ^[26]

Cocaine and comparisons with other evidence

The EUDA reports an NCA assessment of 117 tonnes and £9.4–11.8 billion for Great Britain in 2019, drawing on wastewater, supply evidence and intelligence. NCA director Steve Rodhouse subsequently told Parliament that the UK cocaine market was worth £11 billion. These assessments strengthen the case that cocaine spending can be much larger than older survey-based totals suggest. They are related NCA evidence, however, and should not be counted as two independent confirmations. ^{[13, 14]}

Their broad agreement in scale is informative; their precise agreement is not established. Coverage, reference periods and underlying assumptions differ. Nor should a separate historical crack estimate be added to a newer cocaine estimate that already includes crack. Doing so would manufacture a larger market through classification rather than evidence.

Heroin is the largest unresolved reconciliation problem

The older evidence pack put the opiates market at £3.8 billion in England and Wales. That category and period differ from the newer heroin measure. A simple percentage decline would therefore imply a comparability that the sources do not establish. ^[3]

An independent administrative-data model estimates 310,718 people using opiates and/or crack in England in 2022/23, with a 95% confidence interval of 298,138–326,648. It explicitly warns against comparison with the previous prevalence series because the method changed. This is a count of people, not a spending estimate, and includes crack-only use. ^[17]

The practical question is whether the recent revenue model can be reconciled with plausible expenditure across people using opioids, including those receiving treatment. We cannot answer by multiplying every person in treatment by an assumed daily purchase. Treatment status, frequency, substances and time spent using all matter. Equally, we should not silently replace the new heroin component with an old opiates valuation. A new spending study and transparent biomarker calculations are needed to decide between these possibilities.

4 Cannabis requires a separate estimate

The alternative uses the Adult Psychiatric Morbidity Survey; the lower model uses the Crime Survey for England and Wales and acknowledges underestimation. ^[1] Survey selection materially changes the result.

The IEA’s Joint Venture report is a useful transparent comparator, but it is an older think-tank estimate written in support of legal regulation. Its turnover estimate and its proposed tax revenues are different quantities. Its claim about what a legal market might raise must not be imported into this paper as a measurement of current criminal income. ^[10]

Parey and Rasul’s peer-reviewed study is methodologically valuable because it starts from sales of legal complementary products rather than disclosures of illegal consumption. Its estimates were close to twice standard demand-side estimates for the same years. This gives an independent reason to take survey under-counting seriously. It does not supply a multiplier that can safely be applied to all drugs or to modern cannabis products. ^[11]

The IDMU study supplies a substantially higher historical estimate. Its summary gives an upper value of £8.6 billion, while section 4.4.1 gives £8.8 billion; this internal inconsistency should remain visible. Its caveats include respondent representativeness, small web samples and incomplete usage data. It is unsuitable as a current central estimate without updated, independently representative inputs. Hosting as a BMJ response attachment does not make it a peer-reviewed BMJ study. ^[12]

These figures should be compared as competing models of cannabis consumption. They should neither be summed nor averaged into an apparent consensus. The most useful next evidence would describe spending and quantity by frequency of use, product type and source, including purchases, gifts and personal cultivation.

5 A transparent UK scenario

This is our conditional extrapolation. The geographical uplift is not endorsed by the Home Office. It makes explicit the assumptions required to answer a UK-wide question.

Let S be the six-drug England subtotal and C the cannabis estimate for England and Wales, both in billions of pounds. We assume identical annual spending per resident across the relevant countries, unchanged price relationships, and no additional allowance for omitted drugs or measurement bias. The calculation is:

UK scenario = S × (UK population ÷ England population)
+ C × (UK population ÷ England and Wales population)

The ONS mid-2025 populations, released on 1 October 2026, are 69,483,900 for the UK, 58,834,800 for England and 3,175,200 for Wales. They give multipliers of 1.181000 and 1.120527 respectively. Using this single population vintage keeps the denominators consistent; it does not harmonise the different drug-data periods. ^[25]

For stress tests, we use the reported six-drug margin of ±£4.9 billion. ^[1] Calculations by CLA. Two decimal places show the arithmetic and do not imply accuracy to £10 million.

The narrow £17–18 billion description changes only the cannabis input while retaining central values elsewhere. It is not an uncertainty interval. The wider £11–24 billion stress test also varies S, but it still omits uncertainty in country differences, pricing, coverage and model structure. It is not a UK confidence or credible interval, and neither endpoint is a proven minimum or maximum.

A statistically valid combined interval would require the joint distribution of the component estimates, including their dependence. Adding individual margins does not generally yield a 95% interval for a sum. The report’s published aggregate margin is therefore treated here as a sensitivity input, not re-certified as a probability statement for the whole UK market.

The scenario also inherits mixed price and consumption periods. No CPI uplift to October 2026 is applied. A general consumer-price index cannot tell us how illegal drug prices, purity or purchasing behaviour have changed. A nominal spending estimate may rise because quantities rise, prices rise, or a different part of consumption becomes visible. Those mechanisms should not be conflated.

6 The four nations cannot be treated as identical

Scotland’s dedicated 2009 study valued its 2006 market at about £1.4 billion. It combined prevalence, consumption and prices, including treatment-linked evidence. Heroin represented 39% of expenditure and people classified as problem users accounted for 63%. This is historically informative, but far too old to add to a recent England total. ^[9]

Public Health Scotland’s revised estimate is 43,600 people with opioid dependence in 2023/24, with a 95% credible interval of 42,000–45,400. It covers ages 15–69 and uses linked administrative data. England’s published opiate/crack measure has a different definition and age scope. These figures cannot be converted into national spending ratios without additional assumptions. ^{[18, 17]}

Northern Ireland’s Department of Justice reports Class A and B drug seizures worth more than £26.5 million in its July 2026 update covering 2024/25. That is evidence of enforcement activity, not an annual retail-market valuation. Without a credible interception rate, multiplying it by five, ten or any other convenient factor would be arbitrary. ^[21]

For Wales, the immediate problem is visible in the construction of the newest combined estimate: cannabis includes Wales while the six-drug component does not. For all three nations outside England, a defensible extension should model individual drugs, relevant age groups and use intensity. Applying England’s average to every resident is useful only as a stated scenario.

7 What other evidence can and cannot establish

Surveys and frequent consumption

The latest retrieved Crime Survey release covers the year ending March 2025. It reports drug use by 8.7% of 16–59-year-olds in England and Wales, about 2.9 million people, with no statistically significant annual change. Nearly half of people reporting use said they used only once or twice. The household sample excludes several populations likely to differ in consumption and may also suffer non-disclosure. ^[16]

Prevalence answers how many people used, not how much they bought. A stable number of consumers can coexist with increasing consumption among frequent users. Conversely, more occasional use can increase prevalence with little effect on turnover. Any spending model must separate frequency and quantity, and avoid counting a person’s entire drug budget once for every substance they use.

Seizures and intelligence

Home Office seizure statistics explicitly warn against interpreting quantities seized as a measure of prevalence or availability. In 2024/25 powder-cocaine seizures fell by weight while the number of seizure incidents rose. A few large interceptions, enforcement effort and recording changes can move totals. ^[20]

The NCA’s 2026 assessment judges that the illicit-drugs threat likely increased in 2025 and reports lower wholesale prices. That supports scrutiny of changing supply conditions but does not establish a percentage increase in retail revenue. More abundant supply can increase quantities while depressing prices; the effect on total spending depends on both. ^[19]

Online sales and international markets

RAND’s study of online drug markets found that wholesale transactions were an important revenue component. Adding online-platform turnover to estimated consumer expenditure risks counting goods first online and again when sold offline. Vendor location is also not necessarily the buyer’s location. These data describe distribution channels rather than a separate additive UK market. ^[22]

The EU drugs-market assessment places minimum EU retail expenditure at €31 billion for 2021. This is not a UK estimate and its coverage and methods differ from the English wastewater model. Allocating it to Britain by population or using it to cap the English estimate would be unsound. ^[23]

UNODC’s 2026 evidence places potential global cocaine manufacture in 2024 at about 4,100 tonnes, with a range of 3,800–4,700 tonnes. Global supply evidence helps explain why domestic market conditions may change. It cannot identify the share consumed in the UK, the proportion intercepted or the final retail receipts. ^[24]

8 What the findings mean for public policy

First, market scale and harm require separate accounts. The 2017 Drug Strategy’s £10.7 billion figure referred to social and economic costs in England and Wales. The organised-crime study’s later £20 billion cost figure is also distinct from its sales valuation. Neither is a competing estimate of consumer turnover. Adding either to retail expenditure would require a separate welfare-accounting justification, not simple arithmetic. ^{[27, 8]}

Second, a large market creates substantial revenue opportunities for criminal suppliers, but turnover alone does not reveal how much remains with UK organisations. Imported stock, domestic distribution costs, losses and onward transfers all matter. Nor can we infer the number of people employed or the concentration of market power from the total.

Third, valuation should not determine treatment priorities by itself. A substance can account for a relatively small share of money spent and a much larger share of severe harm. A fall in expenditure is not necessarily a health improvement if it reflects cheaper or more potent products. The relevant outcomes include avoidable harm and access to care as well as market disruption.

Fourth, revenue is not a ready-made tax forecast. A regulated market would have different prices, costs, products, participation and compliance. Tax receipts would depend on policy design and on the share of consumption moving into legal supply. A serious fiscal assessment would model these changes rather than apply a tax rate to today’s illicit valuation.

For CLA, the strongest contribution is to improve the accuracy of the debate. We should make the distinction between measured evidence and inference visible, challenge outdated geographical labels, and press for reconciled estimates. The evidence does not by itself prove that any single enforcement, treatment or legal-regulation policy is best. Those choices require separate causal and welfare analysis.

9 Conclusions and the evidence needed next

This review supports a low-tens-of-billions scale under the newer consumption evidence, while leaving a substantial unresolved conflict with national accounts. The most defensible public approach is to cite the partial official estimate precisely and present the UK scenario as conditional. We do not recommend publishing a single unqualified current UK total.

A stronger national estimate would require the following published work:

• A reconciliation between ONS expenditure, Home Office consumer-spending models and NCA market assessments, showing common periods and definitions.
• Country-specific consumption and spending estimates, by substance, rather than one population uplift.
• Updated purchasing evidence for frequent users and people outside household surveys, with separate measures of purchased, gifted and self-produced drugs.
• Reproducible wastewater conversion and valuation code, including heroin-specific excretion and degradation factors, purity assumptions, price weights and the joint uncertainty of totals.
• A fuller account of omitted substances and illegal medicine diversion, with lawful medical and veterinary use separated wherever possible.
• Separate, linked accounts for consumer expenditure, domestic value added, criminal profits and social costs.

These are research priorities, not assumptions that can be filled with plausible-looking numbers. Until they are resolved, the uncertainty is part of the substantive finding.

Appendix A Review method and limitations

This is a structured public-source evidence review completed on 14 October 2026 and updated on 15 October 2026, not a formally registered systematic review or a claim to have located every unpublished estimate. Searches covered UK market value, retail expenditure, narcotics national accounts, individual-drug valuations, wastewater, consumption, Scotland, Wales, Northern Ireland, online sales and international market studies. Bibliographic references were followed back to original reports wherever accessible.

Official analytical publications, original academic studies and direct testimony were prioritised. Think-tank and specialist estimates were retained with their methods and limitations. News coverage, parliamentary repetitions and commercial market forecasts were not treated as independent estimates when they reused an older source or referred to a hypothetical legal market. This prevents frequently repeated numbers receiving disproportionate weight.

The 1998 estimate is traced through the later Home Office study and the original report’s catalogue abstract; it is not represented as independently recalculated. The NCA cocaine range is attributed to the EUDA’s account of NCA evidence, alongside direct parliamentary testimony. The ONS figures use its September 2026 release. No new survey, confidential intelligence or primary transaction dataset was collected.

Figures are rounded as published unless labelled as CLA calculations. Dates distinguish publication from the period being estimated. The source list below identifies relevant sections so readers can inspect the evidence. The monetary comparison is descriptive; it is not a pooled statistical estimate or a trend series.

Revision record: 14 October 2026 — first publication following source and calculation checks. 15 October 2026 — added the Home Office’s 2021 to 2026 wastewater release as source 29 and explained its implications in section 3. No monetary estimate or scenario calculation was changed. Corrections and additional sources are welcome; any named acknowledgement or quotation from private correspondence will require the contributor’s permission.

Appendix B Sources and verification notes

Sources 1–28 were accessed on 14 October 2026; source 29 was added and accessed on 15 October 2026. Numbers in square brackets refer to the entries below. Each link opens the source or its publisher record. These entries include original estimates, methodological checks and contextual indicators; they are not 29 independent estimates of the same market.

1. Home Office (2026). The proceeds of crime in England and Wales 2023 to 2024. Published 15 September. Section 2.4, Tables 1 and 2; geographical and timing qualifications; alternative cannabis model. Source
2. Home Office (2026). Wastewater Analysis Estimating drug consumption. Published 13 April; updated 8 October. Table 1 and Annexes A and B. Publication history is linked from the report. Source
3. Home Office (2020). Review of drugs Evidence pack, supporting Dame Carol Black’s phase one review. Slides 61 to 64, particularly the explicit England and Wales and 2016/17 labels. Source
4. Office for National Statistics (2026). Consumer trends, series MNC2, 02.3 Narcotics CP NSA £m. Annual 2024 and 2025 observations, release dated 30 September 2026. Current prices; not a GDP value-added series. Source
5. Pudney S, Badillo C, Bryan M, Burton J, Conti G and Iacovou M (2006). Estimating the size of the UK illicit drug market. Chapter 4 in Measuring different aspects of problem drug use, Home Office Online Report 16/06. Printed pages 46–48 and the discussion of baseline limitations. Source
6. Bramley-Harker E (2001). Sizing the UK market for illicit drugs. Home Office RDS Occasional Paper 74. Original report catalogue and abstract; the monetary estimate is also reported in source 5. Source
7. Mills H, Skodbo S and Blyth P (2013). Understanding organised crime Estimating the scale and the social and economic costs. Home Office Research Report 73. Drugs supply section and Annex 2; 2010 market estimate. Source
8. Home Office (2019). Understanding organised crime 2015/16, second edition. Section 2.1, especially 2.1.1 Scale and 2.1.2 Social and economic cost. Distinguishes the £4.5bn market from the £20bn cost estimate. Source
9. Casey J, Hay G, Godfrey C and Parrott S (2009). Assessing the scale and impact of illicit drug markets in Scotland. Scottish Government Social Research. Executive summary and market model; estimates refer to 2006. Source
10. Snowdon C (2018). Joint Venture Estimating the size and potential of the UK cannabis market. Institute of Economic Affairs. Publisher summary of 29 June, including 2016/17 quantity and retail-value calculations. Source
11. Parey M and Rasul I (2021). Measuring the Market Size for Cannabis A New Approach Using Forensic Economics. Economica 88, 297–338. DOI 10.1111/ecca.12354. Final publication uses 2008–09 data. Source
12. Atha MJ and Davis ST (2011). Taxing the UK Cannabis Market. Independent Drug Monitoring Unit, 26 August. Table 11 and section 4.4.1, page 10; sections 10.1 and 10.6, pages 24–25. Upper values differ between the body and summary. BMJ response attachment, not a BMJ research article. Source
13. EUDA / EMCDDA (2022). Cocaine retail markets Multiple indicators suggest continued growth and diversification. National market size estimates section; reports NCA’s 2019 Great Britain assessment and the mixed-methods basis. Source
14. House of Commons Home Affairs Committee (2022). Oral evidence on Drugs, HC 198, 29 June. Steve Rodhouse, National Crime Agency, on cocaine valuation and consumption. Evidence record 10516, question 267. Source
15. UK Parliament (2025). Written question 71709 on illegal-drug market values. Answer by Sarah Jones, 11 September, referring back to the Black review evidence pack. Source
16. Office for National Statistics (2025). Drug misuse in England and Wales Year ending March 2025. Released 11 December. Main points, frequency of use, and data sources and quality. Source
17. Department of Health and Social Care and UK Health Security Agency (2025). Estimates of opiate and crack use in England 2022 to 2023 Main points and methodology. National estimate and methodology-change warning. Source
18. Public Health Scotland (2026). Estimated prevalence of opioid dependence in Scotland 2014/15 to 2023/24. Main points, incorporating the correction of 23 June 2026. Source
19. National Crime Agency (2026). National Strategic Assessment 2026 Harm to individuals. Illicit drugs assessment concerning developments in 2025. Source
20. Home Office (2026). Seizures of drugs in England and Wales Financial year ending 2025. Interpretation warnings and sections 2 and 3 on powder-cocaine incidents and quantities. Source
21. Department of Justice Northern Ireland (2026). Relentless efforts lead to results against organised crime Long. Published 20 July, reporting on the Organised Crime Task Force 2024/25 annual report. Seizure valuations are not total-market estimates. Source
22. RAND Europe (2016). Internet-facilitated drugs trade An analysis of the size scope and the role of the Netherlands. English summary, particularly the discussion of wholesale transactions on page 6. Source
23. EMCDDA and Europol (2024). EU Drug Markets Analysis Key insights for policy and practice. Aggregate estimate refers to 2021 EU retail expenditure. Source
24. UNODC (2026). World Drug Report 2026 data portal. Trends in coca cultivation and cocaine manufacture; estimated potential manufacture in 2024. Source
25. Office for National Statistics (2026). Population estimates for the UK England Wales Scotland and Northern Ireland Mid-2025. Released 1 October. Table 1; all population inputs use the same publication vintage. Source
26. McCall AK and colleagues (2016). Critical review on the stability of illicit drugs in sewers and wastewater samples. Water Research 88, 933–947. DOI 10.1016/j.watres.2015.10.040. University of Copenhagen abstract and bibliographic record. Source
27. HM Government (2017). 2017 Drug Strategy. Introduction, page 6 of the PDF, identifying £10.7bn as social and economic cost in England and Wales. Source
28. Office for National Statistics (2016). National Accounts articles Changes to National Accounts Blue Book 2016 Improvements to household expenditure estimates. Released 30 June; development programme includes narcotics sources and methods. Source
29. Home Office (2026). Wastewater analysis Estimating drug consumption 2021 to 2026. Published 14 October. Sections 1.3 and 2, Table 1 and its footnotes; trends at 16 consistently monitored English sites, not a national monetary valuation. Accessed 15 October 2026. Source

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