But there is a non-statistical basis for concern: an ominous parallel with the financial environment that prevailed in the weeks leading up to the October 1987 stock-market crash. On that day — Black Monday — the Dow Jones Industrial Average dropped 22.6% in a single session.

The dollar headed for its strongest weekly performance in almost three years against other major currencies, maintaining momentum on Friday after U.S. President Donald Trump imposed new tariff rates on dozens of trade partners.