Keeping Track: single-day selloffs

Last week was not a happy one for Worldcom Inc. First, the firm was dropped from the S&P 500 index. Then it watched as its stock, which had already lost 90 percent of its value this year, was sold in record volume. Trading of its stock on the Nasdaq hit a new high of 670 million shares, knocking the price down to $1.24 per share.

Since 1994, the Nasdaq has led in daily volume. It lists more stocks than the New York Stock Exchange, including volatile technology stocks.