India, Aug. 28 -- Have you noticed how a motorcyclist who always wears a helmet on the main road may sometimes ride without one on a quiet road inside your colony? He has not necessarily decided that a head injury is no longer dangerous but simply thinks that the chance of being stopped by a policeman is much smaller.

This is a basic problem with regulation. A rule backed only by the threat of punishment works only if people believe they will be caught. Where enforcement is infrequent, the rational response may be to ignore the rule if the cost of complying is greater than the perceived chance of being punished. This problem shows up in any attempt to regulate for health and safety. We tend to tell people what not to do and punish them w...