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. Stocks fell sharply Monday near the end of what is shaping up to be Wall Street’s worst December since 1931. The economic turmoil was on President Trump’s mind even on Christmas Day, when during an Oval Office appearance, he cast fresh doubt on the record of Federal Reserve Board Chairman Jerome […]