De-merit goods deliver a lower benefit to the consumer than he or she realises at the time of consumption and, given the combination of information failure and negative externalities from consumption, market failures are highly likely to exist and persist in the absence of government intervention. The AQA exam board likes students to draw a diagram where the marginal social benefit of consumption lies below the marginal private benefit. In this edition of the revision guide you will see a diagram where marginal social cost lies above marginal private cost. AQA examiners’ reports confirm that this approach (taught by many) is acceptable for questions on de-merit goods. So sleep easy!