That isn’t true.
Have you considered that New York had the most crimes in the nation, and a 66% decrease in crime there would add significantly to the national decrease.
The city's murder rate fell by 13.7 percent, robbery fell by 14.6 percent, burglary fell by 17.6 percent, and auto theft fell by 23.8 percent.
Giuliani was about as responsible for the drop in crime in New York as Clinton was for the economic growth in the 1990s.