Regulation by prices and by command

Standard economic theory states that regulation by price is more efficient than regulation by command and control. Exceptions may arise if regulators have good knowledge of the supply curve. In practice, though, governments usually regulate by command and control and do so when there is uncertainty about the technology of supply. We show that government may prefer to regulate by command and control when it cares about the investment decisions of a firm.We are grateful for comments by Kenneth Small, the editor, and two anonymous referees.