Single U.S. trade helped spark May’s flash crash

NEW YORK/WASHINGTON, (Reuters) – A computer-driven  sale worth $4.1 billion by a single trader helped trigger the  May flash crash, setting off liquidity crises that ricocheted  between U.S. futures and stock markets, regulators concluded in  a report.

Reuters, citing internal documents obtained from futures  exchange operator CME Group Inc, identified that trader as  money manager Waddell & Reed Financial Inc. The report by the  U.S. Securities and Exchange Commission and the Commodity  Futures Trading Commission did not identify the trader by  name.

The long-awaited report focused on the relationship between  two hugely popular securities — E-Mini Standard & Poor’s 500  futures and S&P 500 “SPDR” exchange-traded funds — and  detailed how high-frequency algorithmic trading can sap  liquidity and rock the marketplace.

“The interaction between automated execution programs and  algorithmic trading strategies can quickly erode liquidity and  result in disorderly markets,” the report said.

The “flash crash” sent the Dow Jones industrial average  plunging some 700 points in minutes on May 6, exposing flaws in  the electronic marketplace dominated by high-speed trading. The  Dow was down nearly 1,000 points at its lowest point on that  day.