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mars 03, 2004
Brottslighet och power laws
Naturartikeln Criminals follow laws of statistics (Philip Ball) handlar om forskning kring den statistiska fördelningen av antal brott som begås av en och samma person.
The best way to combat casual crime is not to search for persistent offenders but to deter people from committing their first crime.
So say researchers at the London-based company Volterra Consulting who have studied the statistics of criminal acts. "The single most important thing is to persuade people not to commit a crime in the first place," says Paul Ormerod of the Volterra team.
Angående den något självklara slutsatsen att man stoppar brottslighet (i det långa loppet) om man förhindrar det första brottet står det följande:
It might seem obvious that the way to cut crime is to stop people from doing it. But their recommendations contrast with some common approaches to crime prevention.
The practice of rooting out key individuals in crime networks might be effective in dealing with large-scale organized crime, says Ormerod, but it will probably not affect casual crime of the sort committed by bored or frustrated young men, which is by far the most prevalent type of criminality.
Forskarna trodde att de skulle hitta en normalfördelning i antal brott per person, men hittade i stället power laws, dvs att många personer begår inga eller få brott medan ett fåtal personer begår många brott.
Instead they found that that crime rates fell into a mathematical pattern called a power law, in which large deviations from average behaviour are more common. In both studies, most of the boys committed no crimes at all. In the Pittsburgh study, quite a few boys reported over 1,000 criminal acts during the study period, while the average number was just 90.
Physicists often find power-law statistics in systems with many interacting parts. This suggests that the young boys in the study are not responding randomly and independently to criminal opportunities that come their way. Instead they are probably influencing one another, presumably through strong peer pressure.
Papret som refereras är
William Cook, Paul Ormerod, Ellie Cooper: Scaling Behaviour in the Number of Criminal Acts Committed by Individuals
Abstract:
We find subtle deviations from power law behaviour in the number of crimes committed by individuals, analysing the two main criminology databases which track this behaviour, the Pittsburgh Young Offenders survey and the Cambridge UK Study in Delinquent Development. The description of the data when the number of boys committing or reporting zero crimes are excluded is different from that when they are included. The crucial step in the criminal progress of an individual appears to be committing the first act. Once this is done, the number of criminal acts committed by an individual can take place on all scales.
Se även
Volterra Consulting
Paul Ormerod som bland annat skrivit den trevliga boken Butterfly Economics : A New General Theory of Social and Economic Behavior. Ormerod nämndes f.ö. i Physics of Society som handlar om Philip Balls kommande bok.
Sist i Statistikknarkande: Antal webb-besökare och power law finns referenser till mer information om power laws.
Uppdatering
Sydsvenskan skriver också om detta i Kriminella helt åtskild grupp.
Posted by hakank at mars 3, 2004 12:57 EM Posted to Komplexitet/emergens
Comments
Det låter lite som nätverksteorien med hubs och förbindelser som Die Zeit skrev om nyligen.
Posted by: Agnes at mars 4, 2004 01:47 EM
Tack för länken Agnes.
Min tyska är väldigt rostig och översättningsmaskinerna vill inte översätta hela artikeln. Vad jag förstår handlar Die Zeit-artikeln om "komplexa nätverk" (med forskare som Barabasi Mark Newman etc). Detta är ett mycket fascinerande ämne.
Det intressanta är att man i Nature-artikeln inte främst rekommenderar den vanliga lösningen att stoppa spridning i sådana komplexa nätverk genom att identifiera och stoppa centralgestalterna (naven). I stället ska man försöka få förstagångsförbrytarna att inte gå "över gränsen":
"""The practice of rooting out key individuals in crime networks might be effective in dealing with large-scale organized crime, says Ormerod, but it will probably not affect casual crime of the sort committed by bored or frustrated young men, which is by far the most prevalent type of criminality."""
Lite fler referenser till komplexa nätverk finns i kategorin "Social Networks/Complex Networks": http://www.hakank.org/webblogg/archives/cat_social_network_analysiscomplex_networks.html
I översikten på http://www.hakank.org/social_network_analysis/social_network_analysis1.html
finns även recensioner av relevanta böcker
Posted by: Håkan Kjellerstrand at mars 4, 2004 08:53 EM