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 2011. Share prices elsewhere have not been bludgeoned quite so badly, but panic is sweeping through markets (see chart 1). Wall Street’s “fear gauge”, the VIX index, which measures expected volatility through the prices traders pay to protect themselves from it, has rocketed to its highest since America’s regional-banking crisis last year (see chart 2).