Synthesis
What we know about SMS reminders in public-sector programs
Across vaccination, court dates, taxes, voting, and benefits — when do text-message reminders move behavior, and when do they fail?
10 experiments synthesized · 8 positive, 1 mixed, 1 null, 0 negative
Few interventions have been tested as widely as SMS reminders. They are cheap to deploy, easy to randomize, and the marginal cost per recipient is near zero — which means agencies have run them everywhere from vaccination clinics to court systems to tax authorities. The result is one of the largest natural experiments in behavioral public policy.
The pattern that emerges is consistent: SMS reminders work when they reduce a specific friction at the moment of decision, and produce near-zero effects when they merely add information to a problem people already understand. The 'what' of the message matters less than whether there is a concrete action the recipient can take, and whether the message arrives in time to support that action.
Effect sizes typically range from null to 5 percentage points on the behavior of interest. That is small, but at the cost of a text message it remains one of the most reliably cost-effective tools available — provided the agency runs the experiment honestly and reports the null results too.
Takeaway
Run an SMS reminder pilot when the underlying friction is forgetting or missing a deadline. Expect a null when the message asks people to do something they were already not planning to do.
The underlying experiments
Positive findings
8 experiments- Positive
SMS Reminders for Childhood Vaccination — Meta-Analysis
Systematic review (international) · Global (multiple countries) · 2024
Effect: RR = 1.11 (95% CI: 1.05–1.17); effect consistent across income settings
- Positive
Buy-Now-Pay-Later SMS Late Payment Reduction
AFM (Dutch Authority for the Financial Markets) + Riverty · Netherlands · 2024
Effect: −20% of customers charged late fees (1 in 5 avoided a fee)
- Positive
Ownership Framing for COVID-19 Booster Uptake
UCLA Health / NIH-funded research · United States · 2022
Effect: Ownership framing: OR = 1.28 vs. no SMS; +11% relative to generic reminder
- Positive
Voter Registration SMS — Local Authorities
UK Electoral Commission / Local authorities · United Kingdom · 2022
Effect: +1.5 to +3 pp registration rate depending on message frame
- Positive
Court Date SMS Reminders to Reduce Failure to Appear
City of New York / ideas42 · New York City, NY, United States · 2015
Effect: FTA reduced by 21%; equivalent to 30,000 fewer arrest warrants annually if scaled citywide
- Positive
Personalized SMS for Court Fine Repayment
UK Courts Service / Behavioural Insights Team · United Kingdom · 2012
Effect: Personalized SMS with debtor's name: £12.87 average payment vs. £4.46 control (189% increase)
- Positive
SMS Wait Time Notifications for NHS Appointments
NHS England / Behavioural Insights Team · England, United Kingdom · 2012
Effect: DNA rate fell from 11.4% to 8.4% (26% reduction); £30 saved per appointment avoided
- Positive
Vaccination Reminders and Incentives — India
J-PAL / Seva Mandir · Rajasthan, India · 2010
Effect: Control: 6% fully immunized; reliable schedule only: 17%; schedule plus lentil incentive: 38%
Open questions
- When does personalization (using the recipient's name, condition, or balance) materially improve over a generic reminder?
- How long does the effect persist — do recipients habituate after the third message?
- Which populations respond more weakly, and is the gap explained by phone access, language, or trust?
If you've run a pilot that speaks to any of these, submit it to the registry.