In almost every appearance as he campaigns for the Republican presidential nomination, Rudolph W. Giuliani cites a fusillade of statistics and facts to make his arguments about his successes in running New York City and the merits of his views.

Discussing his crime-fighting success as mayor, Giuliani told a television interviewer that New York was "the only city in America that has reduced crime every single year since 1994." In New Hampshire this week, he told a public forum that when he became mayor in 1994, New York "had been averaging like 1,800, 1,900 murders for almost 30 years." When a recent Republican debate turned to the question of fiscal responsibility, he boasted that "under me, spending went down by 7 percent."

All of these statements are incomplete, exaggerated or just plain wrong. And while, to be sure, all candidates use misleading statistics from time to time, Giuliani has made statistics a central part of his candidacy as he campaigns on his record.

Another major American city claims to have reduced crime every year since 1994: Chicago. The city averaged 1,514 murders a year during the three decades before Giuliani took office; it did not record more than 1,800 homicides until 1980. And Giuliani's own memoir states that spending grew an average of 3.7 percent for most of his tenure; an aide said Giuliani had meant to say that he had proposed a 7 percent reduction in per capita spending during his time as mayor.

Facts and figures are often the striking centerpieces of Giuliani's arguments. He has always had a penchant for statistics — his anti-crime strategy as mayor was built around a system known as Compstat that closely tracked crimes to focus law enforcement efforts. On the campaign trail he often wields data, without notes, with prosecutorial zeal to hammer home his points.

But in recent days, both Giuliani's Republican rival Mitt Romney and Democrats have accused him of a pattern of misleading figures and have begun to use the issue to try to undercut his credibility.

An examination of many of his statements by The New York Times, other news organizations and independent groups has turned up a variety of misstatements, virtually all of which cast Giuliani or his arguments in a better light. "He's given us a lot of work up until now," said Brooks Jackson, the director of Annenberg Political Fact Check, which is part of, a project of the Annenberg Public Policy Center of the University of Pennsylvania that has corrected statements by candidates in both parties.

"The mayor likes detail and uses it frequently on the campaign trail in ways the other candidates don't," said Maria Comella, a spokeswoman for Giuliani. "And at the end of the day, he is making points that are true."