Agreement between two or more persons to commit an unlawful act or to accomplish a lawful end by unlawful means. Some U.S. states require an overt act in addition to the agreement to constitute conspiracy. Individual conspirators need not even know of the existence or the identity of all other conspirators. In a chain conspiracy the parties act separately and successively (as in distributing narcotics). A civil conspiracy is not prosecuted as a crime but forms the grounds for a lawsuit. In antitrust law, conspiracies in restraint of trade (e.g., price fixing) are rigorously prosecuted. In the U.S. it is common to punish a conspiracy to commit an offense more harshly than the offense itself, but there has been a growing trend to follow the European example and make the punishment for conspiracy the same as or less than that for the offense itself.