IF A country’s exchange rate represents international investors’ confidence in its government’s policies, the markets have given Britain the thumbs-down. So far this year, only the Nigerian naira among major currencies has put in a worse performance.
The decline seems to be accelerating. On October 7th the pound fell from $1.26 to $1.18 against the dollar within a few minutes, with one trade reported below $1.14. The shift occurred during Asian trading, when liquidity in sterling is likely to be thinnest. The most likely explanation for the plunge lies in the action of algorithmic trades—computer programs that automatically buy and sell assets, from currencies to commodities. Such programs may be designed to sell when an asset’s price falls below a certain level. These sales can be contagious, with one program’s trades setting off the sell signals of other algorithms.
The most famous “flash crash” occurred on Wall Street in May 2010, when the Dow Jones Industrial Average fell by almost 1,000 points in the middle of a trading day. On that occasion, the market righted itself before drifting lower in subsequent…Continue reading