NYSE price mix-up causes headaches

October 28, 2011 - 3:45 PM

NYSE Euronext released incorrect price information on more than 1,000 stocks and other securities late Thursday, causing some shares to show price swings that hadn't really happened.

One example was Precision Castparts Corp., which at one point on Friday was supposedly down as much as 9.6 percent. But that was based on an incorrect closing price. In reality, its shares were down about 2.2 percent from their correct Thursday close.

"'Not fun' would be a good description of my entire morning," the company's communications director, Dwight E. Weber, said.

The problem started at 7:27 p.m. Thursday when NYSE's Arca platform sent incorrectly coded share price information. An e-mail sent to traders on Friday said the problem involved prices from aftermarket trades on Thursday that were incorrectly coded as if they had happened during regular trading that day. The e-mail says the mix-up potentially affected the closing price in some shares that trade on the New York Stock Exchange as well as its Arca platform.

The impact was on some stocks, exchange-traded funds, and mutual funds that started with the letters A though T. Symbols starting with U through Z were not affected.

NYSE spokesman Rich Adamonis said more than 1,000 ticker symbols were effected. He said the mix-up is still being investigated.

In the case of Precision Castparts, the erroneous price showed up as an artificially high closing trade — exaggerating the shares' decline on Friday.

Some websites were still showing the wrong closing price for Precision Castparts early Friday afternoon. Adonis said websites have to manually update their databases with the corrected closing prices.