Certainty of enforcement. People are careful to obey a rule punished 100% of the time with a $1 fine. They brush off a 10^-5 probability of a $100,000 loss by t

Certainty of enforcement. People are careful to obey a rule punished 100% of the time with a $1 fine. They brush off a 10^-5 probability of a $100,000 loss by thinking "It won't happen to me."