Governments and others in authority sometimes face important decisions in the absence of direct quantifiable evidence. Expert elicitation methods have been developed to quantify uncertainty in such contexts including estimating risks of volcanic eruptions , climate change  and effect sizes in clinical trials . We report a study using this method to quantify uncertainty regarding the likely impact on smoking rates of plain packaging of tobacco products.
The WHO Framework Convention on Tobacco Control includes packaging as one of the core non-price demand reduction measures, whereby “packaging and labelling do not promote a tobacco product by any means that are false, misleading, deceptive or likely to create an erroneous impression about its characteristics, health effects, hazards or emissions” . Having overcome a high court challenge, Australia is the first to sell all tobacco products in plain packaging (i.e. without brand imagery or promotional text, and using standardised formatting) [5, 6], while the UK government is conducting a public consultation on the possible introduction of such a policy . As yet, however, this measure has only just been implemented by the first country to adopt this policy, so the evidence available to anticipate the impact of such a policy is inevitably indirect. Such evidence includes experimental and observational studies of the impact on attitudes and behaviour of various types of cigarette packaging [8–12].
Two systematic reviews of this indirect evidence have described three ways in which plain packaging may reduce smoking rates, particularly amongst children and young adults: first, by reducing the appeal of packs; second, by increasing the salience of health warnings; and third, by standardising pack colour, thus avoiding perceptions of this as an indicator of product harmfulness [13, 14].
As this evidence is necessarily indirect, its relevance has been questioned (for example, the strength of the relationship between thinking about quitting, a common outcome measure in this set of evidence, and actual quitting), and doubts raised too as to the strength of anti-smoking campaigners’ beliefs about the likelihood that plain packaging will reduce rates of smoking .
At least two recent reports suggest that plain packaging could increase smoking: first, by reducing product differentiation, leading to smokers buying cheaper brands; and second, by increasing smuggling and counterfeit products, thereby increasing the availability of cheaper cigarettes [15, 16]. The assumptions underlying these predictions have, however, been contested . The first of these reports was funded by an organisation that receives some funding from the tobacco industry , the second by the tobacco industry , while the third is funded by a campaigning public health charity, which receives funding from health-related charities as well as the UK government Department of Health .
This study aims to elicit estimates of international tobacco control experts on the likely impact of plain packaging of tobacco products on smoking prevalence in adults and the percentage of children trying smoking. The impact on children is of particular importance given that the majority of smokers first try smoking in adolescence, with nicotine dependence developing rapidly thereafter, even before the user becomes a regular (weekly) smoker .