Two studies in the latest issue of the Journal of Law and Economics cast doubt on whether sex offender registry and notification laws actually work as intended.

One study, by J.J. Prescott of the University of Michigan and Johan Rockoff of Columbia University, found that requiring sex offenders to register with police may significantly reduce the chances that they will re-offend. However the research also finds that making that same registry information available to the broader public may backfire, leading to higher overall rates of sex crime.

Meanwhile, another study by University of Chicago Ph.D. student Amanda Agan finds no evidence that sex offender registries are at all effective in increasing public safety.

Prescott and Rockoff -- Do Sex Offender Registries and Notification Laws Deter Crime?

Using data from 15 states over more than 10 years, Prescott and Rockoff examine the evolution of sex offense rates as states passed and began to enforce their registration and notification laws. Registration laws require that sex offenders check in with and provide information to the police following their release from prison, whereas notification laws make sex offender information available to the public, often via the Internet. The researchers analyze sex offender registration and notification laws separately, which is important because the laws are designed to work in very different ways.

Prescott and Rockoff find that a registration requirement without public notification reduces reported sex crime substantially, most likely through better police monitoring and more effective apprehension of recidivists. For a state with an average-sized registry, a registration requirement reduces crime by about 13 percent from the sample mean. The drop in crime gets larger as registries grow larger, indicating that registry laws lower crime by discouraging registered offenders from re-offending, as opposed to discouraging potential first-time offenders.

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In contrast, public notification laws, such as the listing of released offenders on the Internet, may actually undo some or all of a registry's crime-reducing power. While Prescott and Rockoff discover that the threat of being subjected to notification deters some potential first-time sex offenders from committing crime, released offenders appear to become more likely to do so. In fact, adding public notification to an average state's registration law leads to slightly higher levels of total reported sex crime. Taken as a whole, the research shows that while police registration discourages sex offender recidivism, public notification actually encourages it.

Why would public notification encourage sex offenders to re-offend? Perhaps because they have little else to lose. In particular, notification can make the threat of prison less effective. According to Prescott and Rockoff, their findings suggest that "convicted sex offenders become more likely to commit crimes when their information is made public because the associated psychological, social, or financial costs make a crime-free life relatively less desirable."

J.J. Prescott and Jonah E. Rockoff, "Do Sex Offender Registration and Notification Laws Affect Criminal Behavior?" Journal of Law and Economics 54:1

Amanda Agan -- Sex Offender Registries: Fear Without Function?

Agan finds no evidence that sex offender registries are effective in increasing public safety.

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Her study used three different types of analysis to test the effectiveness of sex offender laws. First, she compared arrest rates for sex crimes in each U.S. state before and after registry laws were implemented and found no appreciable changes in crime trends following the introduction of a registry.

Second, Agan tested whether registries discourage convicted offenders from re-offending. To do that, she looked at data on over 9,000 sex offenders released from prison in 1994. About half of those offenders were released into states where they needed to register, while the other half did not need to register. She could then compare crime rates in the two groups.

She found little difference in the two groups' propensity to re-offend. In fact, those released into states without registration laws were slightly less likely to re-offend.

"The results show that an offender who should have had to register appears to behave no differently, or possibly worse, than on who did not have to register," she writes. "If anything, registered offenders have higher rates of recidivism."

Third, Agan looked at census blocks in Washington D.C. to see if higher numbers of sex offenders in a given block correspond to higher rates of sex crime arrests. She found that crime rates in general, and sex crimes in particular, do not vary according to the number of sex offenders in the area.

The block-by-block analysis was designed to assess "the potential effectiveness of registries by considering whether where offenders live is predictive of where they offend," Agan writes.

"The results show that knowing where a sex offender lives does not reveal much about where sex crimes, or other crimes, will take place," she writes. That result calls into question the rationale for creating registries in the first place.

She concludes that sex offender registries do little to increase public safety, "either in practice or in potential."

Amanda Y. Agan, "Sex Offender Registries: Fear without Function?" Journal of Law and Economics 54:1.