The stock market is going dark thanks to a boom in activity by individual investors and manic trading in stocks such as GameStop Corp.
A record 47.2% of U.S. equity trading volume in January was executed outside public stock exchanges, up from 39.9% a year earlier, according to data from Rosenblatt Securities, a brokerage firm.
Before 2020, the percentage of what is known as dark trading had hovered just below 40% for years. Now, on some days, more than half the shares that change hands in the U.S. are traded on various off-exchange platforms. That happened for the first time on Dec. 23, three times in January, and again on Tuesday, when off-exchange volume hit 50.5%, an all-time high for a single day of trading, Rosenblatt data show.