This is frustrating, because it's not a difficult crime to deter. The gain to the thief is very small, but if the city makes no enforcement effort at all, the

This is frustrating, because it's not a difficult crime to deter. The gain to the thief is very small, but if the city makes no enforcement effort at all, the risk to the thief is even smaller. Some people think that since police couldn't catch a large fraction of the offenders, it's not practical to deter the crime, but this isn't true; all that's needed is to bring the risk into the same range as the gain, which, again, is quite small. So almost any real chance of prosecution is sufficient. I've read that this theory has been verified experimentally, though I don't recall where.