Passage Summary: A new hidden tracking device helps catch car thieves after they've already stolen a car. Even though very few people use it and thieves don't know it's there, car theft has dropped a lot in those areas.

Reasoning: The antitheft device is hidden and does not deter thieves from attempting theft, yet in cities where even a small number of cars have it, overall theft rates have fallen significantly.

Analysis: We are faced with a classic mystery: how can a device that doesn't stop a thief from breaking in—and is only installed in a tiny fraction of cars—cause a massive drop in crime? It’s like finding out that a new brand of invisible vitamins taken by only 1% of the population somehow cured the whole city's flu. To resolve this, look for an answer that explains how catching a few 'experienced' thieves has a massive ripple effect. If a small group of professional thieves is responsible for the vast majority of heists, putting just a few of them behind bars would naturally cause the total numbers to plummet.