Big emerging-market companies worry investors

Since september, when a botched budget in Britain roiled markets enough to threaten giant pension funds, investors have been looking for other vulnerabilities that might cause markets to break. Emerging economies are a prime candidate. Historically, high American interest rates and a soaring dollar have triggered financial instability across the developing world. A few unlucky places, including Argentina and Sri Lanka, have stumbled into crisis this time round, but many emerging-market governments have deeper foreign-exchange reserves and less dollar-denominated debt than before, and thus look much sturdier than even a decade ago.