In a challenge brought by a competing vacuum manufacturer, the National Advertising Division recommended that SharkNinja discontinue a claim that "Americans now choose Shark 2-to-1 over Dyson."

Shark told the self-regulatory body that the term "choose" conveyed to consumers that the claim was based on sales volume, especially as it was accompanied by a conspicuous disclosure of "Unit Sales of Upright Vacuums" located directly underneath the claim in bold, clear, easy-to-read font. Consumers' preference for one product over another can be based on a number of different factors, including total sales, the advertiser said.

The challenger, Dyson, countered that the preference claim lacked support. The reasonable implication of the claim is that Shark conducted some form of consumer preference study to support its comparison, Dyson argued, and the mere fact that one brand happens to outsell another does not, by itself, illustrate that consumers prefer the other brand. Sales data are particularly suspect as substantiation for preference claims, when there is a large difference in price between the products, as in the case between Shark and Dyson, the challenger said.

The self-regulatory body agreed. "NAD reviewed the challenged commercials in their entirety and determined that one of the messages reasonably conveyed is that consumers prefer Shark vacuums over Dyson vacuums—a preference message which goes beyond sales superiority," according to the decision.

Although Shark used the word "choose," when combined with the word "over" the ads indicated "that there is a preference between two options," the NAD explained. Further, "within the context of the commercials which contain numerous performance claims, it is a reasonable consumer takeaway that the choice to purchase a Shark is based on consumers' preference for a vacuum that provides such benefits."

For example, in one Shark infomercial, the announcer touted the benefits of the vacuum by stating that it "has more suction than the newest $700 Dyson Cinetic," "makes my home cleaner and my job easier," concluding with "The Powered Lift-Away is the total transformation of the upright vacuum. It's no wonder that Americans now choose Shark 2-to-1 over Dyson."

"Use of the phrase 'it's no wonder' clearly connects the purchasing decision to the aforementioned attributes, thus conveying that consumers have a preference for Shark vacuums over Dyson vacuums because of such qualities," the NAD wrote.

Was Shark's sales data sufficient to provide a reasonable basis for the claim? No, the NAD determined.

"By its nature, a consumer preference claim connotes that a particular group of consumers (representative of a defined population) have made an identifiable product choice between two or more products based upon a particular product attribute (or attributes)," the NAD wrote. "While overall sales may be one indicia of consumer preference, sales alone are not wholly dispositive of individual preference."

Other variables are at play in consumer preference, such as the cost of the product and the accessibility of obtaining the product, the self-regulatory body noted, as well as the realities of the marketplace, which may sometimes "have a serious effect on the opportunity to choose and, thus, sales may not be a truly accurate barometer of consumer preference."

Given the price difference between Shark and Dyson products, "consumers who buy Shark products are not necessarily choosing them over Dyson," the NAD said. Further, Shark's claim "obscures the fact that the comparison is based purely on sales," the decision added. "The disclosure … is not likely to be understood by consumers to mean that Shark brand outsells Dyson and even if it did, that message is contradictory to the main message that consumers 'chose' Shark 'over' Dyson in a head-to-head selection."

The NAD recommended that Shark discontinue the claim that "Americans now choose Shark 2-to-1 over Dyson," but noted that "nothing in this decision precludes Shark from making a comparative claim based on unit sales (e.g., 'Shark outsells Dyson 2-to-1'), provided that such a claim is accurate and does not imply a head-to-head preference."

To read the NAD's press release about the case, click here.

Why it matters: The self-regulatory body cautioned advertisers that "total sales are not always synonymous with consumer preference," as there are "a number" of variables that influence consumer preference for one product over another, from the cost of the product to the realities of the marketplace. An advertiser's best bet for substantiating a preference claim: "Survey evidence which directly gauges consumer preference among competing products is the most relevant support for a claim that one product is preferred over another," the NAD wrote.