The National Market System (NMS) is a regulatory mechanism that governs the operations of securities trading in the United States. Its primary focus is ensuring transparency and full disclosure regarding stock price quotations and trade executions. It was initiated in 1975, when, in the Securities Acts Amendments of 1975, Congress directed the Securities and Exchange Commission (SEC) to use its authority to facilitate the establishment of a national market system. The system has been updated periodically, for example with the Regulation NMS in 2005 which took into account technological innovations and other market changes.