Van Daele, Stijn

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Ghent University Academic Bibliography

Stijn Van Daele – Mobility and Decay – Ljubljana, 12/09/09 Offender mobility and distance decay: www.ircp.org Universiteitstraat 4, B-9000 Gent, BelgiumAggregated and offender level differencesStijn Van Daele1ESC conferenceLjubljana, 12/09/09Stijn Van Daele – Mobility and Decay – Ljubljana, 12/09/09 Research question• Wim Bernasco (yesterday, Env.Crim.1):o “One of the most important laws – scientific laws –in criminology is distance decay.”•www.ircp.org Universiteitstraat 4, B-9000 Gent, BelgiumIs it?o Is DD a universal law in (enviromental) criminology?o Is offender mobility intertwined with different distance decay patterns? At the aggregate level At the level of the individual offenderStijn Van Daele – Mobility and Decay – Ljubljana, 12/09/09 Background: DD pattern• Most crimes are committed close to home• Gradual decline: the chance of criminal operations is reduced when the distance www.ircp.org Universiteitstraat 4, B-9000 Gent, Belgiumincreases• Prompted by rational choice and routine activities:o Travelling (for crime) takes time, costs and efforts and increases risk.o One will merely travel if profits outweigh costs (Morselli & Royer, 2008; Snook, 2004)3Stijn Van Daele – Mobility and Decay – Ljubljana, 12/09/09 Debate• Many studies have observed such a patterno …be it mostly on an aggregated level• Van Koppen & De Keijer (1997) vs. Rengert, www.ircp.org Universiteitstraat 4, B-9000 Gent, BelgiumPiquero and Jones (1999):o DD is / is not the result of an ecological fallacay and cannot / can be found at both the aggregate and individual level• Smith, Bond & Townsley (2009): two thirds of JTC variation resides between offenders.o It is worthwhile to bring decay analysis down to the level of the individual offender4Stijn Van Daele – Mobility and Decay – Ljubljana, 12/09/09 Our research• Divides distance decay into its two components:o Near home offending: average travelled distances www.ircp.org Universiteitstraat 4, B-9000 Gent, Belgiumare smallo Decay: there is a gradual decline in crime as distances increase• And aims at linking decay to offender mobility.5Stijn Van Daele – Mobility and Decay – Ljubljana, 12/09/09 Method• Property crimes with known offenders• Nationwide (Belgium), but only geographic information on municipality levelwww.ircp.org Universiteitstraat 4, B-9000 Gent, Belgium• 5 ‘mobility’ features (for property crime):o Multiple offending (10 or more) ~ experienceo Co-offendingo Eastern European offenderso Older offenders (age 30 or more)o Offending of affluen target areas ~ ‘rich pickings’ (cfr. Mawby, 2001)6Stijn Van Daele – Mobility and Decay – Ljubljana, 12/09/09 Results (aggregated)• Higher mobility confirmed: mean travelled distances for these offenders were higher than for otherswww.ircp.org Universiteitstraat 4, B-9000 Gent, Belgium• Distance decay was observed for all groups, but deviated slightly for Eastern European offenders7Stijn Van Daele – Mobility and Decay – Ljubljana, 12/09/09 Results (aggregated) www.ircp.org Universiteitstraat 4, B-9000 Gent, Belgium 8Stijn Van Daele – Mobility and Decay – Ljubljana, 12/09/09 Decay at the offender level• Followed a method proposed by Smith et al. (2009):o Calculated skewness estimates and skewness z-www.ircp.org Universiteitstraat 4, B-9000 Gent, Belgiumscores for distances travelled by each individual offendero If right tail of distribution is longer than the left (= positive skewness) -> decayo Significant decay implies a skewness z score > 1,96 (2 standard deviations)• Only for multiple offenders (to overrule the law of small numbers)9Stijn Van Daele – Mobility and Decay – Ljubljana, 12/09/09 Results (individual)Sz > 1,96 0 < Sz < 1,96 -1,96 < Sz < 0 Sz < -1,96All multiple offenders 49,4% 24,7% 14,1% 11,8%www.ircp.org Universiteitstraat 4, B-9000 Gent, Belgium 10Co-offenders 48,5% 26,6% 15,1% 9,5%Eastern European 38,5% 31,1% 19,7% 10,7%Age 30+ 45,8% 25,8% 18,1% 10,3%Attractive targets 46,0% 25,5% 16,2% 12,3%Stijn Van Daele – Mobility and Decay – Ljubljana, 12/09/09 Results (individual)• For only half of the multiple offenders, a significant decay has been observed• For every 5 offenders with significant distance www.ircp.org Universiteitstraat 4, B-9000 Gent, Belgiumdecay, there is 1 with significant distance increase• Sz is negatively correlated with mean distance (r=-.39) -> DD is stronger for offenders who offend near home11Stijn Van Daele – Mobility and Decay – Ljubljana, 12/09/09 Conclusions• Larger mobility may result in different DD patterns• DD has been observed at the aggregate www.ircp.org Universiteitstraat 4, B-9000 Gent, Belgiumlevel…o Although basic group divisions already show certain changes (e.g. Eastern European offenders)• … but cannot be translated straightforward into DD at the level of the individual offendero Many offenders show no significant DD pattern (Sz < 1,96) or even follow a distance increase pattern (Sz < -1,96)12Stijn Van Daele – Mobility and Decay – Ljubljana, 12/09/09 Was Wim Bernasco wrong?• As far as I know, Wim is rarely just 'wrong'• However, DD studies need to take into account particular issues:www.ircp.org Universiteitstraat 4, B-9000 Gent, Belgiumo e.g. previous residenceso Other anchor points• ... and is less universal on more detailed levels of analysis (different groups, individual offenders) than it is on a general level

Offender mobility and distance decay: Aggregated and offender level differences

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Offender mobility and distance decay: Aggregated and offender level differences

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