Goldman CEO Solomon says part of October’s market sell-off driven by programmatic trading

Goldman Sachs CEO David Solomon said Thursday that he believes part of October’s steep stock sell-off was the result of programmatic trading.

“There’s no question when you look at last week, some of the selling is the result of programmatic selling because as volatility goes up, some of these algorithms force people to sell,” Solomon told CNBC’s Wilfred Frost. “Market structure can, at times, contribute to volatility and one of the things that we’re spending a bunch of time thinking about at the firm is how changes in market structure over the course of the last 10 years will affect market activity.”

The major U.S. stock indexes fell sharply earlier this month as investors dumped equities because of fears of rapidly rising interest rates, a possible global economic slowdown and overly ambitious tech valuations. The Dow Jones Industrial Average is more than 1,000 points down from highs earlier in October; the S&P 500 is down 5 percent this month.

The Goldman chief highlighted the rise of a number of relatively new market assets — such as passive index or exchange-traded funds — as examples of the new types of technology that are still being perfected.

“All those things are untested over any duration of time with severe stress,” Solomon said. “Now, when we see a little bit of stress, you can see reactions that might lead you to believe that there’s a risk that with more significant stress that could play a bigger role. I wouldn’t predict that, but it’s certainly something we watch.”

Popular exchange-traded vehicles, such as Vanguard’s Total Stock Market ETF, have swelled in size in recent years as more investors funnel cash into so-called passive funds. Assets under management in the Total Stock Market ETF have buoyed from roughly $86 billion in October 2017 to about $102 billion currently.

Solomon took the helm at Goldman from Lloyd Blankfein at the start of October, marking the beginning of a new chapter in the bank’s 149-year history. Blankfein led Goldman as chief executive for 12 years, guiding the firm through the financial crisis, regulatory oversight and other major challenges on Wall Street.

Solomon, who moonlights as a disc jockey under the the stage name “DJ D-Sol,” has already redesigned the company’s top management since being named heir apparent in July. He is expected to adopt the title of chairman at the start of 2019, when Blankfein officially retires.

WATCH: Watch CNBC’s full interview with Goldman Sachs CEO David Solomon