Habit formation and activity persistence: Evidence from gym equipment

This paper identifies the effect of habit formation on persistence of an important health-related behavior, namely usage of stationary exercise equipment. Exploiting user-activity data from a leading manufacturer and using rainfall as an instrument for initial exercise behavior, we find that frequent early activity leads to more persistent exercise in the subsequent periods, which is consistent with habit formation. Specifically, individuals who exercise one more time per week over a four-week initial period are more than three times as likely to exercise in each of the next eight weeks without missing a week. However, survival probabilities are quite low, consistent with recent experimental work. The primary implication is that for interventions to lead to persistent behavioral change, they must require more frequent activity or longer intervention periods than recent incentive-based field experiments.