Shoppers sort what you say into what they can see, what they’ll learn by using it, and what they’ll never know. They discount the last two, and they’re right to.
A shopper can see a hoodie’s color. They can’t see whether it will pill after ten washes, and they’ll never see where the cotton was grown. Every claim falls into one of those three bins.
Economists named the bins fifty years ago. Phillip Nelson (1970) split product qualities into search qualities, which you can check before buying, and experience qualities, which you only learn by using. Michael Darby and Edi Karni (1973) added credence qualities, which a buyer may never be able to verify even after use: whether a supplement contains what it says, whether a candle was poured by hand, whether a mailer is recyclable in your town Published.
The theory predicts that buyers trust search claims most, because lying about them is pointless. In 1990 Gary Ford, Darlene Smith and John Swasy tested that directly. Consumers were more skeptical of experience claims than search claims, and more skeptical of subjective claims (“luxurious”) than objective ones (“100% cotton”). The researchers didn’t find the extra step they expected for credence claims over experience claims Published. Read that as: once a shopper can’t check a claim before paying, the discount is already applied. It doesn’t matter much to them whether they’ll find out next week or never.
The discount starts the moment a claim can’t be checked on the page.
They look for someone else who has checked. For most DTC products that means reviews: other buyers with no reason to flatter you. PowerReviews, which sells review software, reports that 95% of shoppers consult reviews before buying Reported (vendor data). The other checkers are certifiers, publications, and your own guarantee, which is a claim you pay for if it’s false. A generous return policy says “we’re confident” in a way copy can’t; the returns guide covers what it costs.
That’s why reviews and claims belong in one book. A claim your reviews contradict (“runs small,” says every third review of your “true to size” jeans) costs you twice: the sale, and belief in your next claim.
The Federal Trade Commission’s 1984 policy statement on substantiation says advertisers need a reasonable basis for a claim before it runs. If an ad says or implies a level of support, like “tests show” or “doctors recommend,” the advertiser must have at least that level Published. For health claims, the FTC’s December 2022 guidance sets the bar at “competent and reliable scientific evidence” and says randomized controlled trials are generally what experts would require. Testimonials, however sincere, are not a substitute Published.
Notice the overlap. The claims customers discount most are the ones regulators scrutinize most. Both are reacting to the same fact: only you know whether it’s true.
You can’t make a credence claim checkable, but you can make it more specific, name who checked it, and show the document. Each step moves it closer to a search claim.
| Instead of | Say | Why it works |
|---|---|---|
| Premium cotton | 100% cotton, 280 gsm, knit in Portugal | Objective, and partly checkable on arrival |
| Eco-friendly packaging | Mailer is 80% recycled paper, certified by [scheme]; recyclable where paper is collected | Specific, names the checker, states the limit |
| Clinically proven | In a 12-week randomized trial of 60 adults, [result]. Study summary linked. | Matches the claim to the study, with the size shown |
| Loved by thousands | 4.6 from 2,314 reviews, including 131 one-star. Read them. | Checkable on the page, and the negatives add credibility |
The figures are illustrations and the brackets are placeholders. Never fill them with a number, certifier or study you don’t have on file.
This is one chapter of The Proof File, which is free and readable in full on a single page with no form in front of it.