The new JPMorgan Chase & Co. offices in New York. A run for the exits by investors in levered exchange-traded funds on Friday exacerbated the largest single-day stock market selloff since April, according to strategists at JPMorgan Chase & Co. The S&P 500 Index fell 2.7% in the rout, while the Nasdaq 100 plunged as much as 3.6%, after a social media post by US President Donald Trump threatened fresh tariffs on China. Most Read from Bloomberg Bram Kaplan and colleagues at JPMorgan pinned the blame for t ...