PITTSBURGH — Authorities say crime rates in Pittsburgh dropped for the sixth straight year in 2011, following national trends.

The Pittsburgh Bureau of Police says in its 2011 annual report issued Wednesday that the number of murders fell by 20 percent, assaults fell by 14 percent, and burglary fell by 8 percent.

But rapes increased by 4.5 percent, while arson jumped by 25 percent.

Overall crimes fell from 25,834 in 2002 to 18,704 in 2011.