Note: This advice is given by the CAP Executive about non-broadcast advertising. It does not constitute legal advice. It does not bind CAP, CAP advisory panels or the Advertising Standards Authority.
‘Best-selling’ claims, and other claims which are likely to have the same meaning to consumers, such as ‘leading’ and ‘no.1’ claims, are likely to be considered objective comparisons with identifiable competitors.
The CAP Code requires advertisers to hold documentary evidence to substantiate claims that consumers are likely to regard as objective and that are capable of objective substantiation. Additionally, any comparisons with identifiable competitors must be verifiable and comply with other relevant rules (Rules 3.33 – 3.37). See also Comparisons: Identifiable competitors, Comparisons: General
Is sales data always required?
Substantiation
The CAP Code requires advertisers to hold documentary evidence to substantiate claims that consumers are likely to regard as objective and that are capable of objective substantiation (Rule 3.7).
The nature of the evidence required to substantiate “best-selling” claims, or any claim which is likely to be understood in the same way by consumers, will vary depending on the context in which the claim is made and how it is likely to be understood by its audience. However, it is likely that comparative evidence relating to unit-sales, market share, or both, will be required.
Absolute best-selling claims are likely to be understood as entire market comparisons, and advertisers would therefore need to demonstrate that their product is the best-selling across the entire market, taking into account the products of all competitors.
For example, the ASA determined that the AA’s claim to be ‘The UK’s number 1 breakdown service provider’ would be interpreted as a ‘best-selling’ claim, in other words that the AA had the most members compared to their competitors in the UK breakdown insurance market. The ad was considered misleading, because the AA did not have membership figures of their competitors to compare against their own, meaning the evidence was deemed inadequate (AA Ltd, 20 July 2022).
Conversely, in 2017 the ASA considered that consumers would interpret ‘Richmond, proud to be the nation’s favourite’ to mean that Richmond Sausages were the best-selling sausages in Great Britain. Because the advertiser could show that their sausages were the best-selling in Great Britain, the claim was deemed to have been substantiated (Kerry Foods Limited, 25 October 2017).
By way of further example, the ASA upheld a complaint about the claim “#1 holiday website on the planet”, because the advertiser did not provide evidence to demonstrate that it had the largest turnover of holiday rentals when compared to global competitors (Rental Republic Ltd, 19 January 2022). In contrast, Ryanair’s claim to be “Europe’s number one airline” was not considered misleading. The ASA considered that consumers would likely understand the claim to mean that, over a reasonable period before the ads were produced, Ryanair had carried more passengers than any other European airline. As the advertiser could demonstrate this to be true, the ASA decided the ad was unlikely to mislead consumers (Ryanair Ltd, 7 February 2018).
Marketers must also ensure that the way data is collected for their own sales and competitor sales is sufficient to allow for an accurate comparison. The claim “ST. MORIZ UK’S NO. 1 TAN” was considered misleading because it was not clear if the advertisers’ sales figures were accurate, or if the data had been collected, presented, and applied in a different way to their competitors. In addition, the data had been subject to masking, whereby some retailers did not provide their volume of sales figures for certain products, including St Moriz’s own product, as it was commercially sensitive. Therefore, the data was considered unreliable (Hothouse Partnerships Ltd, 18 April 2018.
Verifiability
The CAP Code requires that comparisons with identifiable competitor products must objectively compare one or more material, relevant, verifiable and representative feature of those products (Rule 3.35).
Marketers do not need to explicitly identify the competitor or product that they are comparing with to be subject to the rules on comparisons with 'identifiable' competitors. If a consumer can identify at least one competitor that is being compared to, whether or not it is explicitly identified in the ad, this will mean that the comparative claims must be verifiable. In most cases, “best-selling” claims are likely to be understood as comparisons with identifiable competitors and must therefore be verifiable.
The information required to make a claim verifiable will depend entirely on the specific comparison and the evidence used to support it. Marketers should include as much information as possible in the ad to ensure that consumers are able to check the accuracy of the claim for themselves, and include a signpost in the ad to further information detailing the basis of the comparison. If verifying the comparison requires specialist knowledge, consumers should be able to get a knowledgeable and independent person or organisation to verify the comparison for them.
The ASA considered that, in the absence of further qualifying information explaining what criteria was used to make the claim, "#1 World's Live-Games Provider" would be understood by businesses to mean that TVBet’s live games offering was the best-selling on the market. The ads did not direct businesses to any additional information regarding the comparisons and explaining the basis for the claims. Consequently, the ASA concluded the ad did not allow the comparisons to be verified and was misleading (ASTOK Ltd, t/a TVBet, 15 April 2020).
See Comparisons: Verifiability.
Is sales data always required?
Whilst in most cases best-selling claims need to be supported by sales data, in some circumstances advertisers may be able to substantiate these claims without holding evidence relating to their competitors’ sales provided they are able to show evidence which demonstrates they are the market leaders.
For example, in 2018, the ASA accepted data comparing an advertiser’s web traffic with that of its competitors over six months. The results showed that the number of unique visitors was more than its four closest competitors combined and more than double the number of total visits than its closest competitor. The ASA considered that, while visitor numbers alone were generally not a guaranteed indication of market share, because the difference in web traffic was so great, in these particular circumstances it was reasonable to infer that the advertiser was the leading provider and had substantiated the claim (Medichecks.com Ltd, 14 February 2018). For more information on this type of comparison, see Web Traffic.