In the past, serious water and air contamination led to the Yokkaichi pollution problem. After the verdict of the trial, those factories that discharged sulfur dioxide gas at levels beyond the environmental standards faced fines or even suspension of operations. While previously, the more they discharged the more their profits rose, things were reversed after the verdict, with those who curbed their discharges becoming more prosperous. Evidence such as this that changes in a society's rules can result in major improvements in environmental quality should be incorporated in the economic development of developing countries.