The sudden plunge of the technology-heavy Nasdaq Composite index into correction territory (defined as a 10 per cent fall from a recent peak) was almost certainly a harbinger of worse to come, but more worrying are less obvious signs of systemic financial problems ahead. There is trouble brewing in emerging markets, which suggests a market rout extending well beyond Wall Street and other advanced markets. Even worse, according to the International Monetary Fund, the fortunes of stock and cryptocurrency markets have now become linked in what could become a mutual spiral. Yet still the idiocy persists in stock markets that…