Report
Phase 4: Illegal Gambling Index – Technical Report
The Gambling Commission’s technical report detailing the development of the Illegal Gambling Index.
Executive summary
This report details the technical approach taken to developing a metric to track consumer usage of illegal gambling websites for the Gambling Commission’s Gambling Survey for Great Britain (GSGB). This report was produced by Yonder Consulting in collaboration with the Commission as part of their Consumer Voice Research Programme.
This report documents the evolution of the question set from initial development and piloting through to the methodology, including refinements informed by subsequent research and testing. The development of the approach represents an important step in strengthening the Commission's evidence base on participation in online illegal gambling in Great Britain. Designed as a flexible and evidence-led measure, the index provides a framework for monitoring consumer engagement with illegal gambling websites and may evolve over time as new evidence, behaviours and market developments emerge.
The Illegal Gambling Index approach
Through conducting a multi-phased research project aimed at understanding consumer engagement in illegal gambling websites, Yonder was able to develop an Illegal Gambling Index to provide the Commission with a metric through which it can track consumer engagement with illegal gambling websites. The aim of the index is to identify varying degrees of confidence in consumer engagement, rather than to provide a definitive measure of illegal gambling participation.
The Index uses survey responses to 7 ‘indicators’ that reflect behaviours associated with gambling on websites that are not licensed by the Commission, and are therefore considered ‘illegal’ gambling websites. To reflect differing levels of confidence that an indicator represents engagement with an illegal gambling website, each indicator was assigned a strength rating (and corresponding numerical score).
3 indicators were classified as Near Certain (score of 3) because they are closely linked to the Commission’s licensing requirements and thus provide a high degree of confidence that the website is operating illegally:
- used a gambling website that you knew was not on Gamstop
- signed up to a gambling website because you knew you wouldn’t need to verify your age or identity
- cancelled a withdrawal before it reached your bank and/or wallet on a gambling website.
3 indicators were classified as Strong (score of 2) as they reflect behaviours that are closely associated with illegal gambling websites but do not provide definitive evidence of engagement. A lower degree of certainty was applied to these measures because respondent misunderstanding, misclassification or inaccurate self-reporting may account for a proportion of reported activity:
- used a Virtual Private Network (VPN) specifically to access a gambling website that was not otherwise available in Great Britain
- placed a bet and/or played a game on a gambling website using cryptocurrency (such as Bitcoin)
- placed a bet and/or played a game on a gambling website using Non-Fungible Tokens (NFTs) or virtual assets.
An indicator was classified as Weak (score of 1) as it may indicate engagement with an illegal gambling website but is subject to a higher degree of uncertainty. This lower confidence primarily stems from the possibility of respondents misreporting payment methods, due to poor recall or due to confusion between credit and debit card use.
Placed a bet and/or played a game on a gambling website using money directly from your credit card (that can be paid off each month) was classified as a weak indicator.
When the survey respondents are asked whether they have ever experienced any of these 7 indicators, they are presented with 6 response options to choose from:
- Yes, in the past 4 weeks
- Yes, in the past 12 months
- Yes, more than 12 months ago
- No, never
- Don’t know
- Prefer not to say.
As the gambling landscape changes, new indicators may be added, and existing indicators may be revised or removed. Accordingly, the scoring framework may be recalculated to ensure the index remains robust, relevant, and capable of accurately capturing consumer engagement with illegal websites.
Respondent Classification
Using the composite index score and the recency of reported behaviours, respondents are classified into 4 groups:
- illegal gambling website users in the past 4 weeks
- illegal gambling website users in the past 12 months
- those demonstrating limited indications of illegal gambling website use (some indicators reported in the last 12 months but insufficient evidence to meet the engagement threshold, or indicators reported only more than 12 months ago)
- those demonstrating no indications of illegal gambling website use.
This approach to classifying survey respondents enables reporting of both likely illegal gambling website users and respondents demonstrating limited indications of engagement, while recognising the importance of behavioural recency when assessing confidence in illegal gambling website engagement.
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Introduction - Illegal gambling technical report
Last updated: 5 November 2026
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