Motor vehicle thefts (per capita) are about one third the level they were in the early 1990s, a drop which is consistent with the Great Crime Decline, the large fall in many crimes since the early 1990s. A lot of ink has been spent trying to explain the great crime decline–abortion legalization, lead abatement, increased imprisonment, more policing–these are just some of the leading theories.

In recent years, however, there has been a notable increased in motor vehicle theft–not back to earlier peaks–but a substantial increase. Theft hasn’t increased uniformly across the board, however. Thefts of Kias and Hyundais have seen massive increases–in some places thefts of these cars have increased by a factor of five or ten in just a few years. The reason is simple–most cars today have electronic immobilizers which mean that without the key present these cars can’t easily be hotwired. Some enterprising thieves, however, discovered that Kia and Hyundai neglected to install these devices and they spread the word through Tik-Tok videos about a method to quickly and efficiently jack these cars.

I propose that the micro can shed light on the macro. Consider the four theories for the great crime decline that I mentioned earlier–abortion legalization, lead abatement, increased imprisonment and more policing. The first two, abortion legalization and lead abatement, are theories about why there are fewer criminals–these theories say that people improved and that is why crime declined. But better people shouldn’t steal any car models, including Kias and Hyundais! Moreover, people haven’t suddenly become worse. Thus, offender-based theories cannot explain the sharp rise in motor vehicle thefts. There have been some changes in punishment, imprisonment and policing, in recent years but these have been slow moving and fairly small and in addition they also don’t explain the rise in Kia and Hyundia thefts in particular.

Obviously, what explains the rise in thefts of Kias and Hyundias in particular is the discovery that these vehicles were unguarded, unprotected and unsecured. Notice that being unguarded, unprotected and unsecured swamped any effect coming from abortion legalization, lead abatement, increased imprisonment or more policing.

The failure of the big four to explain the rise in Kia and Hyundai thefts isn’t proof that these theories are wrong. But lets ask the inverse question, can the rise in Kia and Hyundai thefts suggest an explanation for the great crime decline? In other words, can we explain the great crime decline by an increase in security. Begin with the most direct case, motor vehicle theft. Car immobilizes and other security devices began to be installed in the 1990s so the timing fits. Moreover, the timing fits multiple countries. One of the weaknesses of theories of the great crime decline such as increased imprisonment and policing is that these theories work for the United States but the crime decline occurred in many industrialized countries at about the same time. Canadian crime rates, for example, fall in near lockstep with US rates but with very different prison and policing strategies. Immobilizer technology, however, happened at similar times in similar places and where we saw delays or early adoption we also see delayed or early falls in motor vehicle theft. In addition, motor theft declined first for newer cars (secured) rather than for older cars despite the fact that the newer cars are the more desirable for thieves–again this fits the security hypothesis better than an offender or punishment hypothesis.

The security hypothesis fits motor vehicle theft but the connection is less clear with respect to other crimes. Home security devices have increased and become higher quality over time but the change was less rapid and less precisely timed to the early 1990s. The rise of credit cards and decline of cash could have reduced muggings, although again the timing doesn’t appear to be precise. Violent crime would seem even less likely to be security related–although cameras and lights surely matter–but keep in mind that a lot of violent crime is a side-effect of property crime. Vehicle thefts, muggings and drug deals turn into homicides, for example. In addition, there are “life of crime” or “career” effects. If you make motor vehicle theft and burglary less profitable that makes a life of crime less profitable which can reduce crime in general even without specific deterrence.

Overall, the security hypothesis carries some weight, especially in explaining multiple countries. I don’t fully discount any of the major theories, however. Multiple causation is important.

The main less I draw is this: The increase in Kia and Hyundai thefts suggests that the crime wave declined not because the ocean became more gentle but because we built more secure sea walls. The big waves are still out there in the vast ocean and if we lower the walls we shouldn’t be surprised if another big crime wave comes rolling in.