Simulation of an Artificial Society with crime and punishment José Roberto Iglesias, Instituto de...
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Transcript of Simulation of an Artificial Society with crime and punishment José Roberto Iglesias, Instituto de...
Simulation of an Artificial Society with crime and
punishment José Roberto Iglesias,
Instituto de Física e Faculdade de Ciências Econômicas, UFRGS,
Porto Alegre, Brasil
econofis’10, são paulo, march 2010
Co-authorsCo-authors
• Viktoriya Semeshenko (Buenos Aires)• Jean-Pierre Nadal (Paris)• Mirta B. Gordon (Grenoble)
Gordon, Iglesias, Nadal, Semeshenko, Crime and Punishment: the economic burden of impunity, European Physical Journal B 68, 133–144 (2009)
Crime is as old as Crime is as old as humankind humankind “Passional (non-rational) crimes”:
a) Cain and Abelb) Don José and Carmen
Economic crimes a) Jacob and Esaub) Ronald Biggs and the Great Train
Robbery (8 august 1963)c) Bernrad Madoff and “financial
pyramids”(2009)
Crime is as old as Crime is as old as humankindhumankind “Passional (non-rational) crimes”:
a) Cain and Abelb) Don José and Carmen
Economic crimes a) Jacob and Esaub) Ronald Biggs and the Great Train
Robbery (8 august 1963)c) Bernrad Madoff and “financial
pyramids”(2009)
Multidisciplinary explanations and Multidisciplinary explanations and “solutions” for crime: philosophy, “solutions” for crime: philosophy,
law, sociology, ethics, economics...law, sociology, ethics, economics...
Crime and punishment: Crime and punishment: the economic burden of the economic burden of
impunityimpunity The main hypothesis of the model:Crime, particularly economic crimes – stealing, robbery -
has an economic mobile.Each person is characterize by an “honesty” coefficient
that, when high, has dissuasive effect of the decision of committing an offense.
This “honesty” label is a global characterization of education, risk-aversion, fear, moral standards, fear, etc…
The probability of punishment depends on the stolen amount.
Offenders are punished, if caught, with fines an prison, both proportional to the stolen amount.
The average honesty of the population changes as a function of the perception of the society of the level of control of criminality.
Becker’s UtilityBecker’s Utility
(exp)(exp) BootyfWpBootyU kcast
)(BootyE
HU
k
k
ep
We add the “honesty” factor as an additional constraint
)()( BootyEfWpBootyEU kcast
Initial configurationInitial configuration• Each agent i is characterized by
a monthly wage Wi [Wmin,Wmax] triangular, [1,100]
a time-dependent honesty index Hi [Hmin,Hmax] triangular, [0,100]
When and how a crime is When and how a crime is committed?committed?
Criminal attempts
At each attemptselect potential criminal k and a victim v
success of the attempt depends on k’s honesty and the expected gain or booty* (cf. *G.Becker, P. Shikida)
If the crime is performed the offender gets S and the victim losses S
So that
• Crime: k robs a victim a random amount – S ≤ Kv !
H
NNmA inmates
11)(
WfWpWU kcast 55
WS 5vWrndS 10
W
U
H
H
k eepk
5
Arrested offenders and Arrested offenders and punishmentpunishment
Probability of punishment:• p0 – … of small offences
• p1 – … of large offences
Offender k goes to prison for months
Retribution: Offender k pays a fine f x S,
W
SS
e
pppS
1
)( 101
WS /1
Monthly resultsMonthly results
• Simulation setting:• N=1000, 240
months, Nc=5%• S=r*10*Wv, f=0.25S
• Various p0, p1
Crime and punishment: Crime and punishment: resultsresults
averages over 240 months
Left: With prison after-effects Right: Without
HysteresisHysteresis
What happens if the probability of punishment What happens if the probability of punishment changes in time?changes in time?
ConclusionsConclusions There is a first order phase transition in the criminality as a function of the probability of punishment This transition is accompanied by changes in the assets and inequality of he full society. Honesty coefficient (education) is an essential ingredient, along with the economic motivation of crime Punishment is not just fines and prison but also economic aftereffects. The after-effects of prison may increase criminality. If prison do not recover the offenders, crime is the only issue
Ongoing and upcoming…Ongoing and upcoming…• Rehabilitation: effects of incarceration on
honesty indexes and wages• Treatment of recidivism• Underlying networks (social and criminal)• Comparison with the empirical data
• Data from Rio Grande do Sul: correlations between size of the city, average education and criminaliry.
• Shikida interviewed inmates in Paraná: Economic crime is the rule. But criminality seems not to be correlated with poverty
• It is difficult to obtain the fraction of punished crimes to evaluate p0 and p1