Why fear is sweeping markets everywhere

How quickly the mood turns. Barely a fortnight ago stockmarkets were on a seemingly unstoppable bull run, after months of hitting new all-time highs. Now they are in free fall. America’s Nasdaq 100 index, dominated by the tech giants that were at the heart of the boom, has fallen by more than 10% since a peak in mid-July. Japan’s benchmark Topix index has clocked losses well into the double digits, dropping by 6% on August 2nd alone—its worst day since 2016 and, following a 3% decline on August 1st, its worst two-day streak since...