The record volumes aren't an indicator of volatility alone since the Dow industrials and S&P 500 reached new all-time highs last week. They also reflect a sea change in the way trading is done—through online trading programs used by a growing number of large institutional investors including mutual funds and hedge funds in the past five years.
"The days when humans traded with each other are gone. Now computers trade with each other," says James Angel, associate professor of finance at Georgetown University's McDonough School of Business. "Computerized systems are capable of handling big spikes in volume with minimal problems."
For Chris Concannon, executive vice-president of NASDAQ Transaction Services, heavy trading volume is an indication of the increasing efficiency with which the market is now able to execute trades, whether through online brokers or institutional investors using algorithms and electronic trading systems to place orders. Much of that has to do with technology, but it's also a function of much lower trading costs compared with 5 or 10 years ago. "If you can trade for $5, you may be inclined to trade in and out of positions on volatile days. There are very low costs for brokerage fees," he says.
Investors' ability to get in and out of positions all day owing to electronic trading programs means that record volume doesn't necessarily point to broader participation in the market. "Bigger institutional players like hedge funds that have that capability can bang in and out of the market a couple times a second," notes Rueckert. "Even though the same computer systems are trading back and forth, it's going to drive trading volume through the roof."