ARTICLE SYNOPSIS ...Velocity of the S&P 500 by Robert A. Wood Structural changes in security markets resulting from the introduction of derivative instruments, namely options and futures, have been the focus of extensive study in recent years. More recently, the introduction of portfolio insurance and arbitrage trading strategies involving market indices implemented with program trading have been the subject of widespread concern, especially after the events of October 19, 1987. Do derivative instruments, portfolio insurance trading strategies and/or the ability to instantly trigger a large number of trades by ...