By Andrea Shalal WASHINGTON (Reuters) -Central bankers must be persistent in fighting broad-based inflation, International Monetary Fund chief Kristalina Georgieva said on Wednesday, conceding that many economists were wrong when they predicted last year that inflation would ease. “Inflation is stubborn, it is more broad-based than we thought it would be,” she said, adding, “And what it means is … we need central bankers to be as stubborn in fighting it as inflation has demonstrably been.” If fiscal policy and monetary policy worked well, next year might prove less painful, she said at an ev…