In a field experiment at a car wash, 300 customers received loyalty cards requiring 8 paid visits for a free wash — 34% finished when the card had 10 spaces with 2 already stamped, compared with 19% given 8 empty spaces and exactly the same reward.

The offer was eight paid car washes followed by one free wash. Yet the appearance of the loyalty card changed how many customers reached the reward, even though the purchase requirement stayed the same.

Joseph Nunes and Xavier Drèze’s 2006 Journal of Consumer Research paper reported a field experiment that randomly distributed 300 cards at a professional car wash in April 2004. Half had eight empty spaces. Half had ten spaces with two promotional stamps already attached.

During nine months of tracking, 34% of customers with the pre-stamped card redeemed the reward, compared with 19% of those starting with an empty card. The authors called the phenomenon the endowed progress effect: presenting a task as already underway can increase persistence toward finishing it.

The starting line moved on paper

Both groups still needed eight purchases. The pre-stamped version displayed 20% completion at the outset, while the other displayed none. The difference in reported redemption rates was 15 percentage points.

That distinction is the experiment’s central strength. A discount, a cheaper service or an easier qualification requirement could each change customer behavior for straightforward economic reasons. Holding the required purchases and reward constant makes the presentation of progress the feature of interest.

It also gives a business a more precise question to test than whether customers like bonuses. Does a particular way of showing the journey change follow-through when the underlying deal remains equivalent? The answer can be measured through behavior, rather than inferred from whether a design looks encouraging.

The number of remaining purchases was unchanged.

Related research found the finish line mattered

A separate 2006 study by Ran Kivetz, Oleg Urminsky and Yuhuang Zheng examined the goal-gradient hypothesis in consumer settings. Participants in a café rewards program bought coffee more frequently as they approached a free drink.

The researchers also compared a standard ten-stamp card with a twelve-stamp card carrying two bonus stamps. Customers given the apparent head start completed the ten required purchases faster. Another part of the research found increased participation as online song raters approached a reward.

These results concern the relationship between perceived distance and effort. They are related to the car-wash finding, but they are separate experiments with different tasks and outcomes. Faster completion and a higher proportion completing are both relevant to a rewards program, without being interchangeable measures.

For anyone interpreting a dashboard, that distinction matters. A design could bring an existing purchase forward without producing another purchase overall. It could increase completion among existing participants without attracting more people to join. The measurement needs to match the claim.

Progress looks different early and late

In her Chicago Booth teaching material on monitoring progress, motivation researcher Ayelet Fishbach describes the small-area principle. Early in a bounded task, focusing on completed actions can make the next step feel consequential. Later, focusing on the small amount remaining can serve the same purpose.

Her explanation concerns proportional impact. Moving from one completed step to two doubles the visible accomplishment; moving from two remaining steps to one halves the visible distance. The arithmetic offers different ways to frame the same next action.

This does not mean every progress display should automatically switch at its midpoint. It suggests a design hypothesis that can be evaluated in context. A beginner deciding whether to continue and an experienced participant nearing a reward may respond to different information, even within the same program.

The experience between rewards still matters

Progress toward a distant prize is only one part of persistence. Research by Kaitlin Woolley and Fishbach examined immediate and delayed rewards across five studies involving activities such as studying, exercise and eating vegetables.

The work found that immediate rewards were more strongly associated with actual persistence than delayed rewards. Enjoying the activity along the way could matter even when a longer-term benefit was the reason for setting the goal.

Applied to a service business, that suggests examining the experience of each visit as well as the prize at the end. This is an inference for product design, not a result showing that enjoyable car washes caused the loyalty-card effect. Different mechanisms may contribute to repeat behavior and deserve separate tests.

Completion is useful evidence, but not the whole business

A company applying this idea should keep the qualification rule easy to understand and compare equivalent offers. Then it can track the outcomes it actually cares about: completion, time between visits, total purchases, reward costs and whether customers return after redeeming.

Those measures answer different questions. Redemption shows that someone reached a threshold. Retention shows what happened afterward. Profitability depends on the costs and revenue associated with those actions. A successful result on the first measure does not settle the other two.

The practical lesson is to make the hypothesis concrete and the comparison fair. A visible head start is a testable feature of an offer, not a substitute for understanding why customers find the service worth using.

A loyalty card records progress; a business still has to earn the next visit.