One of the nation's leading economists, who admitted to underestimating how well New York would do in recent years, predicted a strong future for the city as international demand for its business services increases. Mark Zandi, the chief economist for Moody's, said in a speech Wednesday in midtown that city-based firms should have plenty of clients around the world in the coming years for advertising, accounting, legal and financial consulting services. "It's always done better than I anticipate," said Mr. Zandi of the city during an appearance sponsored by the Urban Land Institute. He noted its recent job growth of about 2.5%, approximately a point higher than the national figure. "And it's happening without financial services" contributing, he noted. "I'm actually quite optimistic about New York City's economy."