The Baltimore Police Department has for the past four years recorded the highest percentage of rape cases that officers conclude are false or baseless of any city in the country, according to The Baltimore Sun's review of FBI data. More than 30 percent of the cases investigated by detectives each year are deemed unfounded, five times the national average. Only Louisville and Pittsburgh have reported similar numbers in the recent past, and the number of unfounded rape cases in those cities dropped after police implemented new classification procedures. The increase in unfounded cases comes as the number of rapes reported by Baltimore police has plunged — from 684 in 1995 to 158 in 2009, a decline of nearly 80 percent. Nationally, FBI reports indicate that rapes have fallen 8 percent over the same period.