The factors that have contributed to the adoption of high-speed trading and affected market structure in recent years include competition, technology, and regulation. The unexpected ways in which these dynamic forces are coming together raise a number of important policy issues.

A handful of high-frequency trading firms accounted for an estimated 70 percent of overall trading volume on U.S. equities markets in 2009. One firm with such a computerized system traded over 2 billion shares in a single day in October 2008, amounting to over 10 percent of U.S. equities trading...

A number of recent technology-related snafus have focused attention on high-speed trading and affected investor confidence in the markets. These incidents and the resulting losses highlight the need for risk controls at every step of the trading process.