The National Market System (NMS) is a regulatory mechanism that governs the operations of securities trading in the United States.[1] Its primary focus is ensuring transparency and full disclosure regarding stock price quotations and trade executions.[1] 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.[2]