Laws requiring sex offenders to register with local authorities are meant to discourage them from moving into the neighborhoods, but the latest study shows they may not be having the desired deterrent effect.

The research provides new information on the contentious question of whether public sex offender registries and housing restrictions actually improve public safety. Housing restrictions typically bar offenders from living near schools, daycare centers or other sites likely to have a high concentration of children who may become victims. As of 2011, nearly 750,000 registered sex offenders were listed in the U.S., whose names can be searched in state and federal registries. But the latest analysis shows that offenders change residences frequently and that over the course of a 30 month period, a third will move into areas where they are not legally allowed to live.

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Researchers led by Alan Murray of Arizona State University studied over 1,000 registered offenders in Hamilton County, Ohio, in the Cincinnati region, at four time periods between 2005 through 2007. They found that in 2005, 41% of sex offenders in the registry lived in a restricted zone, but after December of 2006, only 30% did.

The authors suggest that this 11% reduction resulted from “more stringent enforcement of registry restrictions,” which involved actual evictions carried out under an initiative of the local sheriff and prosecutor. Another factor that might account for some of the decrease included the passage in 2006 of the Adam Walsh Act, which received wide publicity and created a national registry that requires the most risky offenders to sign in and update their information every three months.

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But enforcement isn’t always possible, and other findings in their data make the research far more equivocal. The first was that 65% of offenders moved at least once during the 2.5 year study period, and prior research suggests that not having stable housing increases the risk of offending or failing to register.

Second, many of these offenders resided in marginal and chaotic neighborhoods— which are often the cheapest and least restricted to offenders— and can increase recidivism in several ways. Parents are often unable to supervise children adequately due to long work hours and lack of affordable daycare, making the children more vulnerable. These areas also tend to have more crime and less economic opportunity overall, both of which can affect recidivism.

But perhaps even more concerning was that a third of offenders moved into restricted zones during the study period. It’s possible the trend isn’t significant; many rehabilitation and support services that offenders are mandated to use are located in restricted zones, and the offenders may simply move to these neighborhoods for convenience.

Looking more closely at the offenders who move to restricted areas, however, 51% of those who registered only once and then failed to comply again lived in these regions, compared to 30% of those who registered faithfully. That could suggest that those who are seeking to hide their activities, presumably in plain sight, are moving to these areas, possibly to find new victims.

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So do sex offender registries work to protect public safety? The authors conclude “The present study highlights… that despite these increasingly stringent laws, sex offenders move freely about communities and continue to reside in restricted areas. This mobility suggests that current policies may require modification in their design and implementation to achieve their intended goals.”

Overall, data on the effectiveness of sex offender registries hasn’t been conclusive; while a 2009 review conducted by the Washington State Institute for Public Policy found that registries had no effect on recidivism, for example, that data was not strong enough to be definitive. A 2008 analysis by the National Bureau of Economic Research concluded that registration deters first time offenders but increases recidivism in those who have already been registered, by limiting their ability to get jobs and rehabilitate themselves.

Based on the findings, it’s likely that registries and residence restrictions alone cannot stop the sexual abuse of children. To do that, researchers need far more understanding about what drives this criminal behavior and what type of rehabilitation actually works.

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