Overseas Turbulence Keeps Large-Cap Stocks Up All Night: Chart

The U.K.’s market-rattling vote to secede from the European Union reinforced a trend that’s been lashing U.S. investors since August: news from overseas is jolting S&P 500 Index stocks overnight to an extent that’s almost identical to moves in smaller, less liquid shares that have been historically more volatile during off hours. The swings began converging in 2015 for the first time in at least 15 years, and now the two are the closest they’ve ever been, said Ana Avramovic, equity strategist at Credit Suisse Group AG.