> We should expect the same percentage of people to not report crime when there are 1,000 car break-ins per month as when there are 100
This ignores changes in police enforcement and prosecution of crimes. If there is very little overall crime and the police have the time to find the perpetrator, and the prosecutor agrees to bring charges, you're more likely to report the crime. If there is high crime, police are too swamped to deal with yet another break-in, and the DA is too busy dropping felonies to misdemeanors or not bringing charges at all, then people aren't going to bother reporting crime as much anymore.
This ignores changes in police enforcement and prosecution of crimes. If there is very little overall crime and the police have the time to find the perpetrator, and the prosecutor agrees to bring charges, you're more likely to report the crime. If there is high crime, police are too swamped to deal with yet another break-in, and the DA is too busy dropping felonies to misdemeanors or not bringing charges at all, then people aren't going to bother reporting crime as much anymore.