CRIME’S ECOSYSTEM
Marcus Felson
School of Criminal Justice
Rutgers University
felson@andromeda.rutgers.edu
DIMACS talk
New Brunswick, May 21, 2007
1
Plan for today
I talk fast
A. Orientation
(five slides)
B. Fundamentals of Crime Ecology
(five sides)
C. Crime Foraging
(ten slides)
D. General Theory of Crime Ecology
(seven slides)
E. Baby Mathematics
(we’ll see)
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Part A – Orientation
On five slides
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A1: Not Obvious
• We can’t build criminology on a few bad men
• Nor a few bad areas of town –
– Traditional “ecology of crime” (1930s) large “social
areas” within cities
– But recent data and theory show very local variations
– A high crime area contains low and moderate crime
areas!
• My goal: To be obvious afterwards
4
A2: Not Simple
• Illegal activities feed off legal activities
• Local crime is part of a system of activities
• That means we need ecology
• Not natural for criminologists or police to
study crime as a system
• Not natural for ecologists, biologists, to
include crime
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A3: Not Metaphorical
a. I’m using
ecological concepts
broadly but literally
b. I imagine the“Life
sciences” to be
larger than what you
learned in school.
Life science,
as you probably
see it
Life
science,
as I see it
Criminology
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A4: Not Automatic
•
•
•
•
We can’t do exactly what you do today
Look back a few hundred years
My favorite biologist: Linnaeus
We have to be true to our topic
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A5: Not Genetic
• Useful topics: foraging, defense, symbioses, habitats,
crime settings
• Less useful topics: differential reproduction or mortality
• Species is not the unit – crime applies to all homo sapiens
• Our task: To describe and catalogue illegal activities,
not species.
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Part B – Fundamentals of Crime
Ecology
On five slides
9
B1: Crime is ordinary
a)
b)
c)
d)
e)
f)
g)
Thousands of thefts for every murder
Thousands of quarrels for every escalation
Booze abuse > extreme-drug abuse
Most crime in gang areas is non-gang
“Organized crime” seldom very organized
Stealing password from your desk
Even serial killers follow routines, geo-models
To understand most crime, stop watching television
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B2: Crime is highly physical
• Best predictor of burglary rate 1947-1977:
weight of smallest TV in the Sears Catalogue
• Convergence & Divergences
• Physical, but not mechanical
• Offenders make decisions; motives can vary
• Life sciences or physics ?
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B3: The Crime Triangle
r
fen
et
Of
n
dia
de
ar
rg
Ha
Gu
Ta
nd
ler
Who are the Major Players?
Place
Manager
When offenders & targets come
12
B4: Each crime has a sequence
Murder isn’t a crime: It’s an outcome.
13
B5: Crime is symbiotic in three ways
Crime is
symbiotic with
Examples:
Other criminal
activities
Burglars help each
other find victims.
A drug addict feeds
off shoplifting.
Marginal
activities
A legal prostitute
sells illegal drugs.
Legal
activities
A lawyer nibbles
from a trust
account.
An hourly hotel
houses illegal
prostitutes.
A restaurant
welcomes local
drug dealers .
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PART C
Crime Foraging
Nine slides sum up three dense
chapters in my book,
CRIME AND NATURE
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C1: Not all offenders forage
•
•
•
•
Two guys fight in a bar
Family violence seldom requires foraging
Insiders often can steal without foraging
But foraging still very important
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C2: Standard foraging principles fit
offending (with nuances)
• Offenders minimize the effort
• Offenders minimize the risk
• Offenders maximize the reward**
**But not long-term rewards or punishments!
Plenty of empirical verification
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C3: Offenders are relative generalists
Offender
Versatility
Fairly versatile
Use this to
reduce crime
Hunting method Fairly versatile
Remove easy
crime options
Range
Narrow the
range of targets
**
18
Diet breadth
Not very
versatile**
Reduce targets,
crime benefits
C4: Offender awareness space
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C5: Repeats
• A good deal of repeat victimization – same
residence or business
• Poisson distribution over time, wider
interval
• Near repeats, next door or two doors down,
Poisson distribution over space
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C6: Offenders forage for items
they can carry or overcome
• Here I am stretching “bigger than his head”
• Applies to personal and property crimes
• An offender overcomes personal reach with
– Accomplices
– Vehicles
– Tools
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C7: Offenders minimize
handling time
•
•
•
•
Handling stolen goods
When traveling farther, expect greater gains
These rules assist crime prevention.
“Opportunity Makes the Thief” correct
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C8: Foraging affected by risks
•
•
•
•
•
Other offenders ***
Police, security (who also forage)
Victims, or bystanders
Offenders are risk-takers, but go only so far
Drug abuse cycles affect risk-taking
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C9: Settings rich in crime targets invite
New offenders
Occasional offenders to activate
Active offenders to become more efficient
Returning offenders to stop being so good
A lot of people commit a little crime.
This adds up.
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C10: Sex and foraging
• People seeking sex or social life are highly
vulnerable to crime victimization
• The sexual urge helps lure victims, trick
them, distract them, embarrass them, etc.
• Any sexual rulebreaking is risky: the
offender knows the victim won’t report
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Part D
Building General Crime Ecology
A 400 page book in
Seven Teaser Slides
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D1: Eight primary defenses against crime
Go over these fast
1.
2.
3.
4.
5.
6.
7.
8.
Avoidance
Camouflage
Batesian mimicry
Müllerian mimicry**
Warnings
Physical defenses
Group defenses
Vigorous recovery
Walk in safer areas
Dress like a student
Look tough
Wear gang colors
Put up warning sign
Locks, bolts, armor
Walk in a pack
Sell more, swamp thefts
** My favorite – no time to go over now
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D2: Seven secondary defenses apply, too
but I’ll move on unless you stop me
•
•
•
•
•
•
•
Move away from adversary
Communicate ability to escape
Distractions, feigns, and startles
Symbiotic protection
Chemical and weapon defenses
Sudden weaponry
Emergency social defenses
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D3: Three types of Crime Mutualism
Again – This fits larger ecology
Exchange resources:
Stop mutual enemies:
Spread and reproduce:
Drug buyer & drug seller
Gangs & drug dealers vs.
police
Entertainment newspaper
that advertises prostitutes
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D4: Aegism and crime
(my favorite)
barnacle, whale
Helping offender
move about
Mass transit, lifts
from friends
Epizoism
Find quick refuge
Cavernous public
housing
Phoresis
coral reef
Inquilinism
good bacteria
Endoecism
hermit crab
Find shelter in site Soliciting inside
still used
train stations
Find shelter in
abandoned site
Drug abusers in
abandoned
building
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D5: Three Types of Crime Habitat
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D6: Fragmentation
• Ecologists warn against forest fragmentation
• But we WANT crime’s habitat to be
fragmented!
• We want to reduce crime’s biodiversity
• When a local “colony” dies out, we don’t
want it to recover
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D7: Urban Policy Strategy
• Keep narrow crime habitat from thickening
• Keep two narrow crime habitats from growing
together
• Try to fragment thick crime habitats that
already exist
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Part E
Baby Mathematics
Simple ideas, easily complicated
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Problem 1: How did this happen?
Note five open-air
drug markets of
varying sizes
They grew outwards,
producing a thick
crime habitat
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Prob. 1, cont.
Fractal-like
spread of drug
markets
George Rengert’s
ideas, my version
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Prob.2: Abandoning & Supervising Space
One abandonment
encourages another, and
all encourage crime
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Prob. 3: One crime leads to another
– Direct burglary multiplier model
The sequence:
1.
2.
3.
4.
a burglary occurs, property is taken.
the burglar sells these stolen goods,
to someone who knowingly buys them
who re-sells these stolen goods continued>
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Prob. 3, Cont: The Accounting
Initial burglaries
1,000
Subtract cash burglaries
-580
Non-cash burglaries
420
First sale of stolen goods
406
First purchase of stolen goods
406
Resale of stolen goods
365
Total crimes generated
2,177
CRIME MULTIPLIER =2.177
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Prob. 4: Easy Needle Policy
• Vancouver’s easy needle policy probably
improves safety for current drug abusers at
any given injection.
• But it also seems to draw other drug
abusers to Vancouver!
• New Jersey is adopting parts of such a
strategy
• Unfortunately, drug abusers are a hard
population to trace, but here’s my thinking.
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Prob. 4, cont: Disaggregate
Disaggregate The Population Of Drug Abusers
Tt=
N t=
Total drug abuse population in year t
New local drug abuse population in year t
Mt=
Dt =
Deaths of local drug abuse population in year t
Desisting local drug abuse population in year t
It=
Ot=
In-migration of drug abusers to local area in year t
Out-migration of drug abusers from local area in year t
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Prob 4, Cont: Basic Equation
(a) T t = T t-1 + N t - M t - D t + I t - O t
Rearranging,
(b) T t = (T t-1 + N t + I t) - (M t + D t + O t )
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Prob 4: Explained
In other words, this year’s drug abuse population is augmented by
three components and depleted by three other components.
Augmenting the drug-abuse population:
Last year’s surviving local drug abuse population,
New local abusers, and
In-migration of abusers to the local area from elsewhere.
Depleting the drug-abuse population:
Deaths of local drug abusers,
Desistence of local drug abusers, and
Out-migration of local drug abusers.
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Thanks to those who lasted
Marcus Felson
felson@andromeda.rutgers.edu
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