Researchers pre-stamped loyalty cards and doubled completion

Loyalty punch cards were everywhere — buy eight car washes, get the ninth free — but completion rates were quietly dismal: most cards were lost, forgotten, or abandoned a few stamps in, because eight blank boxes in a row look like a long, undifferentiated slog with no sense of how far along the customer already is. Marketing researchers Joseph Nunes and Xavier Drèze suspected the problem wasn't the number of purchases required, but how the starting line was framed.

They ran a field experiment at a car wash, handing customers one of two loyalty cards. Both required the same actual number of future purchases to earn a free wash. The only difference was the card's face: one showed eight empty boxes to fill; the other showed ten boxes, with two of them already stamped.

The two-stamp head start was entirely artificial — both groups had to buy exactly eight more car washes to earn the free one. But the ten-box card with two pre-filled stamps reframed the task from 'start collecting' to 'you're already 20% of the way there,' converting an identical amount of remaining effort into visible, banked progress.

Pre-stamped two of ten boxes on the card, so the identical eight remaining purchases felt like finishing a task already 20% done, not starting one.

The pre-stamped card reframed the task from 'start collecting' to 'you're already 20% there'.

Loss aversion makes abandoning a card with stamps feel like forfeiting progress.

Both groups faced identical remaining effort, isolating the psychological effect.

The head start cost only ink, not margin, yet outperformed real discounts.

To boost completion of multi-step tasks, start the progress bar above zero—it costs little and reframes the task as continuing, not starting.

34% completed the pre-stamped ten-box card vs. 19% for the blank eight-box card — an 80% lift from two stamps of ink. Nunes and Drèze published the finding as the 'endowed progress effect' in the Journal of Consumer Research in 2006, and it became a standard tool in loyalty-program and habit-app design — from coffee cards issued with a stamp already on them to fitness apps that show a progress bar starting above zero — wherever a company wants to convert a long blank task into a race already underway.