Market Insider

Why new Dow stocks could add to market volatility

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Nike, Visa and Goldman Sachs join the Dow 30 at a historically bad time for the stock market, and they could make it even more volatile.

The stocks were rallying Tuesday, but their gains could be short-lived, analysts say. The changes to the index, effective Sept. 23, include the exit of Alcoa, Hewlett-Packard and Bank of America. Only Bank of America was trading higher Tuesday.

The triple expiration of equity options and futures takes place the Friday before the index changes are to be made.

"The week after triple witching is the worst of all four" weeks of September directionally, said Jeff Hirsch, editor-in-chief of Stock Trader's Almanac. The Dow was lower in 19 of the last 25 years, with an average decline of 1.1 percent, he said.