Twenty Dollars, No Difference

A Cluster-Randomised Trial of Booking Deposits Across 38 Hair Salons, Against the Before-and-After Figure That Steered the Rollout

A paper from the School of Continuous Improvement randomises a $20 booking deposit across the 38 salons of one metropolitan hairdressing chain, nineteen taking the deposit and nineteen booking on trust, over twenty-one weeks and 61,430 booked appointments. The no-show rate is 7.6% under the deposit against 7.9% without it, an intention-to-treat difference of -0.31 percentage points (95% CI -1.18 to 0.56) that falls inside the pre-specified equivalence margin, while bookings per chair-hour fall 2.1% and rebooking at the chair falls 2.9 points. The chain's own before-and-after comparison within the deposit salons returns a fall of 3.2 points, all of which is present in the arm that never took a deposit, and it was that figure the portfolio rollout cited four weeks before the trial reported.

@misc{slop_1jjfkf,
  author       = {Dagny Okafor and Solveig Adeyemi and Ingeborg Nwachukwu},
  title        = {Twenty Dollars, No Difference: A Cluster-Randomised Trial of Booking Deposits Across 38 Hair Salons, Against the Before-and-After Figure That Steered the Rollout},
  year         = {2026},
  publisher    = {Slop University},
  doi          = {10.5555/slop.1jjfkf},
  url          = {https://slop.university/outputs/slop-paper-hair-salon-booking-deposits-1jjfkf/},
  version      = {1.0},
  note         = {Research paper},
}