The scarcity principle says people value something more when it seems limited in supply, time or access.
Robert Cialdini's summary is that "people want more of those things they can have less of".
In A/B tests, real scarcity cues often lift sales, but fake, aggressive or badly placed ones regularly lose.
This page covers the research behind scarcity and urgency, then what 30-plus tests in our database show about when it works and when it backfires.
For the full lists of tests, see the low-stock and scarcity hub, the countdown timer hub and the sales and urgency hub.
The scarcity principle: what the research shows
Scarcity is one of Cialdini's principles of influence, but the idea is older.
Psychologists call it commodity theory: anything that can be owned, is useful and can be passed on gains value when it becomes unavailable.
The cookie jar study
The best-known experiment is Worchel, Lee and Adewole (1975).
Participants tasted chocolate chip cookies from a jar holding either 2 or 10 cookies, then rated them.
- Cookies from the scarce jar were rated more desirable than cookies from the full jar.
- Cookies that went from plentiful to scarce were rated higher than cookies that were scarce all along.
- Cookies that became scarce because of high demand were rated higher than cookies that became scarce by accident.
That last finding matters most for websites. Scarcity works best when it also signals that other people want the thing, which is why "selling fast" copy overlaps with social proof.
How big is the effect?
Michael Lynn's 1991 review of the commodity theory literature pooled the early studies and found a reliable but small effect of scarcity on perceived value (r = 0.12, as reported by later reviewers).
A larger 2022 meta-analysis by Barton, Zlatevska and Oppewal covered 416 effect sizes from 131 studies.
It found the type of scarcity matters by product:
| Scarcity type | Example on a site | Worked best for (Barton et al., 2022) |
|---|---|---|
| Demand-based | "Selling fast", "200 sold this week" | Utilitarian products |
| Supply-based | "Only 5,000 made", "Limited edition" | Experiences |
| Time-based | Countdown timers, "Sale ends Sunday" | High-involvement products |
What the research does not tell you
Most of these studies measure ratings and stated purchase intentions in controlled settings, not revenue on a live store.
A small average effect in a lab says little about whether your timer will beat your control.
That is a question for an A/B test, and the tests below show results in both directions.
Scarcity marketing: real limits, stated plainly
Scarcity marketing means telling shoppers about a real limit on stock, editions or access.
The cleanest wins in our database share one thing: the limit was true and the copy was calm.
- Visually reports that Odd Muse added a subtle, factual "X left" line below the CTA and saw a +22% conversion rate. A more aggressive urgency version tested first did poorly. This is vendor-published, with no sample size given.
- Oliver Kenyon tested authentic scarcity messaging on product pages for a brand whose strategy is built on limited stock, forecasting +$46,900 per month.
- Domaine's test for Tuckernuck showed a size-based "Only X left!" message tied to the size the shopper picked, with an estimated uplift of about $899K a month (an estimate, published by Visually).
- Blend Commerce ran limited-time copy on seasonal coffees without a discount for Stone Creek Coffee: +16% conversion rate, +15% revenue per visitor and +18% add-to-cart. No significance was stated.
The oldest example is MarketingExperiments' "Only 5,000 copies" test for National Alert Registry, where orders of a free DVD went from 0.0189% to 0.115% (+508%).
Treat it as a story, not proof: several things changed at once and the two versions went out as separate emails, not a simultaneous split.
@oliverkenyon
@DaveDiederen
Blend Commerce
Visually@DaveDiederen
Clean CommitScarcity bias: when "almost gone" makes people hesitate
Scarcity bias is the tendency to overvalue something because it seems rare.
It is a cognitive bias, not a law, and on a store it competes with other worries: will my order go through, can I exchange it, is this a trick?
Several tests in our database show low-stock warnings losing:
- Dave Diederen tested "In Stock" instead of "Almost Out of Stock" on a Shopify brand. The calmer message won with +16.78% revenue per visitor, +5.72% conversion rate and +10.46% AOV.
- Clean Commit added a prominent low-stock announcement bar to product pages: -17.5% conversion rate and -11.3% revenue per visitor. The test was short (5,161 visitors over 6 days), with a 93.8% probability the control was better.
- Clean Commit's "high demand" message in the cart reached 141,998 visitors and showed +2.7% conversion rate, but it was not significant. A big sample and still no clear answer is a result too.
The pattern is that scarcity framed as reassurance ("in stock, ships today") can beat scarcity framed as threat.
That fits loss aversion cutting both ways: the fear of missing out can push a purchase, but the fear of a bad purchase can stop one.
A note on honesty
Convertibles reported that a stock meter on a golf brand’s product page beat a "High demand" banner by +26.4% revenue per visitor (368 vs 297 orders, 98% probability to beat control).
Their own caveat says the meter ran on a timer, not live inventory.
A win like that is a short-term number with a legal and trust risk attached, covered below.
FOMO marketing: social proof plus scarcity
FOMO (fear of missing out) marketing combines two signals: other people are buying, and you might miss your chance.
The cookie study's demand finding is the research version of this.
- ConvertPolo added social proof and scarcity messages next to add-to-cart and reported +25% add-to-cart rate.
- ConvertPolo also tested low-stock and scarcity messages in the cart for Sparify: +16.49% conversion rate.
- Dave Diederen changed "Low stock" to "Low stock - selling fast" under the add-to-cart button, adding a demand cue to a supply cue: +2.50% revenue per visitor.
Not every FOMO badge moves anything. Clean Commit's "Selling fast" badge on product cards showed +5.9% conversion but was unproven, and a mobile redesign of the same badge came in at -0.9%, flat.
Badges are cheap to add, so test whether they earn their space.
Urgency marketing: countdown timers and deadlines
Urgency is time-based scarcity: a sale that ends, a shipping cutoff, a cart held for 10 minutes.
It has the widest spread of results in our database, and market, page and price point all seem to matter.
Where timers have won
- Visually reports Benchmade's countdown to the Christmas 2-day shipping cutoff lifted revenue per session +32.4%. The deadline was real and useful to the shopper.
- Dave Diederen added an "order reserved" checkout timer for US brands: +9.50% conversion rate and +4.83% revenue per visitor, with AOV down 4.26%.
- Dave Diederen also placed a countdown timer where heatmaps showed shoppers were focused: +20.65% revenue per visitor.
Where timers have lost
- Dave Diederen's countdown timer for a European market lost badly: -35.61% revenue per visitor and -17.35% conversion rate. Their post says timers often hurt outside the US across 20+ brands tested.
- Kasper Dolk's team removed a countdown timer from checkout after a survey said it felt like too much pressure for a Dutch audience. Removing it won: +25.61% conversion rate and +26.18% revenue per visitor.
- Another checkout countdown timer from Dave Diederen lost with -7.1% revenue per visitor and -5.4% conversion rate.
- Ruben tested a countdown timer across several brands: about +10% conversion on a low-priced brand, no clear lift after 4 weeks on a high-priced one, and -9% on another.
Placement matters even with the same message. Conversion Fanatics found an urgency message above and below the order form won +41%, while the same message only above the order button lost, with the control converting 32% better.
Fake urgency is a legal risk, not just a test variant
A Princeton and University of Chicago crawl of about 11,000 shopping sites found 393 countdown timers, and 157 of them on 140 sites were deceptive: they reset or the offer stayed valid after the clock hit zero.
The FTC's 2022 staff report names countdown timers designed to make consumers believe they only have limited time as a dark pattern.
In the EU, the Unfair Commercial Practices Directive's blacklist bans falsely stating that a product will only be available for a very limited time to rush a decision.
See dark patterns for the wider list. The practical rule: if the deadline or stock number isn't true, don't ship it, whatever the test says.
How to test scarcity and urgency fairly
- Use only real limits: live inventory, real sale end dates, real shipping cutoffs.
- Measure revenue per visitor, not just conversion rate. Checkout timers can raise conversion while cutting AOV.
- Segment by market. A win with US shoppers may be a loss in Europe.
- Test placement separately from the message. The same urgency line can win or lose depending on where it sits.
- Size the test before you start with a sample size calculator and check statistical significance before calling it. Several scarcity tests above were short or unproven.
For more on why these cues work, browse the psychology section.