No mood effects in the field: The case of car inspections

We study mood effect in the field to measure its economic impact and address shortcomings in the existing literature, which typically uses one single mood proxy and ignores selection effects. Using over 50 million car inspections in Sweden and England and multiple mood proxies, we study whether car inspectors are more lenient on good mood days and if car owners self-select into those days. We find evidence of a “Friday effect” in England and a small selection bias, but no support for consistent mood effect. Our findings highlight the importance of considering the expectations of rational actors who may exploit mood effect and the need to study mood in the field using different settings and multiple proxies to avoid hasty conclusions.