A nice fact, and one that seems too neat to be true: theft of motorbikes declines when the law requires helmets. The idea is that you might pinch a motorbike if you saw it left unattended. But if you don’t happen to be carrying a helmet, it’s going to be much harder to ride away on it:
After Texas enacted its universal helmet law, motorcycle thefts in 19 Texas cities decreased 44 percent between 1988 and 1990, according to the Texas Department of Public Safety. Motorcycle thefts dropped dramatically in three European countries after the introduction of laws that fined motorcyclists for failure to wear helmets. In London, motorcycle thefts fell 24 percent after Great Britain enacted a helmet law in 1973. The Netherlands saw a 36 percent drop in thefts in 1975 when its law was enacted. And in former West Germany, where on-the-spot fines were introduced in 1980, motorcycle thefts plummeted 60 percent [source]
The implication, surprising to me, is that most motorbike theft had been opportunistic. Getting hold of a helmet doesn’t seem a very high bar for the would-be thief.