What happens when a government enacts and enforces a mandatory helmet law for motorcycle riders? According to criminologists, a reduction in motorbike theft follows. The 1989 study Motorcycle Theft, Helmet Legislation and Displacement by Mayhew et al. (paywalled, see Wikpedia summary) demonstrated this effect empirically looking at crime figures from Germany, where not wearing a helmet on a motorcycle is being fined since 1980. This lead to a 60% drop in motorcycle theft – interestingly, with limited compensation by increases in other types of vehicle theft.
The plausible explanation: motorcycle thieves incur higher risk of being caught when riding without a helmet after a spontaneous, opportunistic theft. Adaptation is possible but costly and risky, too: looking for loot with a helmet in one’s hand is more conspicious, and preparing specifically to steal bicycles reduces flexibility and narrows the range of possible targets.
Just came across a crime science paper that expresses an idea similar to my security property degrees:
»In addition, for any crime, opportunities occur at several levels of aggregation. To take residential burglary as an example, a macro level, societal-level cause might be that many homes are left unguarded in the day because most people now work away from home (cf. Cohen and Felson 1979). A meso-level, neighborhood cause could be that many homes in poor public housing estates once used coin-fed fuel meters which offered tempting targets for burglars (as found in Kirkholt, Pease 1991). A micro-level level cause, determining the choices made by a burglar, could be a poorly secured door.«
(Ronald V Clarke: Opportunity makes the thief. Really? And so what?)
Clarke doesn’t elaborate any further on these macro/meso/micro levels of opportunity for crime. Maybe I’m interpreting too much into this paragraph, but in essence he seems to talk about security properties – he is discussing in his paper the proposition that opportunity is a cause of crime and reviews the literature on this subject. Opportunity means properties of places and targets.