The car wash experiment
In 2004 two researchers handed out 300 loyalty cards at a professional car wash and then watched what happened for nine months. Every customer was offered the same deal: buy eight washes, get the ninth free.
The only thing that differed was the card. Half the customers got a card with eight empty spaces. The other half got a card with ten spaces, two of which were already stamped when it was handed over. Both groups had to buy exactly eight washes. The reward was identical. The effort was identical.
34% of the pre-stamped group finished the card. Only 19% of the empty-card group did. Nearly double, from a change that cost the business nothing.
Nunes and Drèze called this the endowed progress effect: people given artificial advancement toward a goal work harder to reach it. A card that starts at 2 of 10 feels like something already underway. A card at 0 of 8 feels like something not yet begun, even though it is objectively the better deal.
What does this mean if you run a small service business?
The practical lesson is not “give away two free washes.” It is that visible progress is the mechanism, and most paper punch cards destroy it. A card in a wallet is only visible when the customer happens to look at it, and it is invisible to you entirely. You cannot see who is one stamp away.
- Start the card, do not start it empty. If you want nine paid visits, print an eleven-space card and stamp two at issue. The maths is the same and the completion rate is not.
- Make the remaining distance obvious. Six filled dots and three empty ones says more than the number 6 does.
- Know who is close. The customer at 8 of 9 is the one worth a nudge. On paper you have no way of knowing who that is.
Is retention worth the trouble at all?
The foundational work here is Reichheld and Sasser’s 1990 study in Harvard Business Review, which found that cutting the customer defection rate by 5% raised profits by between 25% and 85%, depending on the industry. For an auto-service chain specifically, the figure was 30%.
One caution, because it is widely misquoted: you will often see this cited as “25% to 95%.” The original range was 25% to 85%, and the top of it came from a single bank branch system. The honest version is still a strong argument — just not as strong as the internet version of it.
How Returnpass does this
A loyalty pass in Returnpass counts up to a reward you define, and lives in the customer’s Apple Wallet rather than their glovebox. They see filled and empty dots every time they open it. You see a “rewards ready to claim” count on your dashboard, so the customers who have earned something are never a surprise at the counter.
If you would rather sell visits up front than give them away, read the guide to prepaid packages, which is the other half of the same idea.