Clean environments as a social norm: a field experiment on cigarette littering

Cigarette littering in public spaces is an environmental and aesthetic problem. Broken windows theory posits that visible signs of anti-social behavior such as littering create the perception of a social norm in built environments. Cigarette butts on the ground then encourage people to drop theirs as well. We test this theory on benches of a university campus in a field experiment with two treatments: (1) a clean environment with no cigarette butts on the ground and (2) a dirty environment with 25 cigarette butts on the ground. Our outcome variable is the number of additional cigarette butts on the ground after two hours. We find a small effect of approximately 0.5 butts less per 2-hour period on clean grounds. Increased cleaning efforts can thus reduce littering, but the effect is probably too small to justify additional cleaning costs.