There was an empty lot in a middle$-$class neighborhood, maintained by a nearby resident. That man moved away, and within a few weeks several bags of garbage and some old furniture were sitting in the lot. Then an old car was parked in the lot and teenagers started to gather there to drink beer and hang out. Within a few months, there was a mugging by the lot and the police made a handful of arrests for drug dealing there. This series of events is an illustration of theory.