The Stock Markets and Automated Trading

There’s a continuing debate about the role of technology in stock market movements. Many blamed the extent of the 1987 crash on program trading that kept triggering more selling as the previous sales pushed down market prices. In the latest episode, Paul Tudor Jones, a famous and successful hedge fund manager, said that forced trading by risk parity portfolio strategies will trigger the next market slide.

This article explains Jones’ argument and the response of critics.

Jones, who oversees $10 billion in his Greenwich, Connecticut-based Tudor Investment hedge fund, is the latest active asset manager to whip up fears surrounding the automated strategies that were a favorite target of bank researchers during the selloffs in August 2015 and early 2016. The strategy has less than $150 billion invested in it, according to data provider eVestment, most of at AQR and Bridgewater Associates’ All Weather Fund.

That’s significantly lower than the roughly $500 billion that some have estimated. And of that total, only around a third is investing in equities, Mendelson said. That compares to the nearly $2 trillion in market value that evaporated from U.S. equities during the last stock market correction.

“Even on a sharp move in the stock market, the positioning changes would be utterly trivial and would have about zero impact,” Mendelson said.