What is Social norm?
A social norm is an unwritten rule about how people in a group are expected to behave. In behavioral economics, the key insight is that beliefs about what others do (descriptive norms) and what others approve of (injunctive norms) powerfully shape individual behavior, often more than personal preferences or incentives.
How it works
Cialdini’s focus theory of normative conduct distinguishes between descriptive norms (‘most people do X’) and injunctive norms (‘most people think you should do X’). Both influence behavior, but they can conflict. Telling hotel guests that ‘most guests reuse their towels’ (descriptive) is more effective than ‘please reuse towels to help the environment’ (injunctive without social proof).
Applied example
A utility company that includes a smiley face on energy bills for households using less than their neighbors reduces consumption by 2-4%, while including a frowning face for high users has a smaller effect because it can inadvertently signal that high usage is normal.
Why it matters
Social norms are one of the most reliable levers for behavior change at scale, but they must be deployed carefully to avoid the ‘boomerang effect’ where telling people what most others do can inadvertently license bad behavior among those already doing well.
