A global economy that until recently was humming has broken down, a sharp contrast to the picture just a year ago when the world was experiencing its best growth since 2010 and seemed poised to do even better .
Already, builders in the United States are erecting fewer single-family homes. German factories are sputtering, and in China, retail sales are growing at their slowest pace in 15 years.
The sudden slowing has fed into a global financial sell-off that has driven several U.S. stock indexes into or near “bear market” territory with losses of more than 20 percent.