I've heard Britain does some tinkering with the crime statistics.
The "tinkering" you mention consists of downgrading crimes (calling a burgulary simple vandalism, and mugging and rape reduced to minor assault), the english police also classifying multiple crimes as a "single crime" (if four apartments broken into they make one report of the incident, four people robbed... one report) and they have gotten to the point where they now "refuse to take a crime report on assaults and muggings".
The mayor of Atlanta Georgia perfected this last tatic. We had a rental truck broken into in front of our hotel in Atlanta. We needed a police report for the insurance and two different police officers refused to write a report. We were told to "phone it in".
After three calls and an hour and a half on hold the lady reluctantly took the report. I found out later that the new practice of "no reports" lowered the citys crime rate since no report, no crime.