"... triggered what appeared to be a 9.6 percent plunge yesterday in an exchange-traded fund that tracks the Standard & Poor’s 500 Index, a drop that would have erased $7.9 billion from one of the most popular securities in the U.S. Data published by the electronic venue at 4:15 p.m. New York time showed the SPDR S&P 500 ETF Trust at $106.46, compared with its opening level of $117.74."
According to the NYSE:
"On Monday, October 18, the 4 pm ET closing auction in NYSE Arca primary listed symbols was delayed due to an issue with a software release, causing the auction cycle to run at 4:15 pm ET. These auction prices, occurring at 4:15 pm ET, constitute the official exchange closing prices for these issues, with the exception of ‘SPY.’ All trades in the closing auction in ‘SPY,’ which occurred at a price of $106.46, were ruled to be broken by NYSE Arca Market Management. The official closing price will be marked at [4:15 pm] utilizing the valid prior print of $118.28."
The S&P index fund (SPY) affected has a market value of some $80 billion, Bloomberg says.
This latest problem comes on the heels of the report on the NYSE flash crash in May which was also traced to a software issue. Investor confidence in the stability of stock markets, which was already suffering, will not be increased by this latest problem.
Robert N. Charette is a Contributing Editor to IEEE Spectrum and an acknowledged international authority on information technology and systems risk management. A self-described “risk ecologist,” he is interested in the intersections of business, political, technological, and societal risks. Charette is an award-winning author of multiple books and numerous articles on the subjects of risk management, project and program management, innovation, and entrepreneurship. A Life Senior Member of the IEEE, Charette was a recipient of the IEEE Computer Society’s Golden Core Award in 2008.