The sell-off triggered a surge in a derivatives index that investors use to hedge against losses, pushing it up by the most since at least 2011, prices compiled by Bloomberg show. The credit-market meltdown was the culmination of a week in which investors withdrew the most cash in at least 10 years from U.S. funds that buy corporate bonds and loans.
https://finance.yahoo.com/news/credit-market-endures-worst-day-172026613.html
