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CRIME’S ECOSYSTEM. Marcus Felson School of Criminal Justice Rutgers University DIMACS talk New Brunswick, May 21, 2007. Plan for today I talk fast. A. Orientation (five slides) B. Fundamentals of Crime Ecology (five sides)

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crime s ecosystem


Marcus Felson

School of Criminal Justice

Rutgers University


New Brunswick, May 21, 2007

plan for today i talk fast
Plan for todayI 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)

a1 not obvious
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
a2 not simple
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
a3 not metaphorical
A3: Not Metaphorical

a. I’m using ecological concepts broadly but literally

b. I imagine the“Life sciences” to be largerthan what you learned in school.

Life science,

as you probably

see it

Life science,

as I see it


a4 not automatic
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
a5 not genetic
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.

b1 crime is ordinary
B1: Crime is ordinary
  • 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

b2 crime is highly physical
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 ?
b4 each crime has a sequence
B4: Each crime has a sequence

Murder isn’t a crime: It’s an outcome.

part c crime foraging

PART CCrime Foraging

Nine slides sum up three dense chapters in my book,


c1 not all offenders forage
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
c2 standard foraging principles fit offending with nuances
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

c5 repeats
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
c6 offenders forage for items they can carry or overcome
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
c7 offenders minimize handling time
C7: Offenders minimize handling time
  • Handling stolen goods
  • When traveling farther, expect greater gains
  • These rules assist crime prevention.
  • “Opportunity Makes the Thief” correct
c8 foraging affected by risks
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
c9 settings rich in crime targets invite
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.

c10 sex and foraging
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
part d building general crime ecology

Part DBuilding General Crime Ecology

A 400 page book in

Seven Teaser Slides

d1 eight primary defenses against crime go over these fast
D1: Eight primary defenses against crime Go over these fast
  • Avoidance Walk in safer areas
  • Camouflage Dress like a student
  • Batesian mimicry Look tough
  • Müllerian mimicry** Wear gang colors
  • Warnings Put up warning sign
  • Physical defenses Locks, bolts, armor
  • Group defenses Walk in a pack
  • Vigorous recovery Sell more, swamp thefts

** My favorite – no time to go over now

d2 seven secondary defenses apply too but i ll move on unless you stop me
D2: Seven secondary defenses apply, toobut 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
d3 three types of crime mutualism
D3: Three types of Crime Mutualism

Again – This fits larger ecology

Exchange resources: Drug buyer & drug seller

Stop mutual enemies: Gangs & drug dealers vs. police

Spread and reproduce: Entertainment newspaper that advertises prostitutes

d6 fragmentation
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
d7 urban policy strategy
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
part e baby mathematics

Part E Baby Mathematics

Simple ideas, easily complicated

problem 1 how did this happen
Problem 1: How did this happen?

Note five open-air drug markets of varying sizes

They grew outwards, producing a thick crime habitat

prob 2 abandoning supervising space
Prob.2: Abandoning & Supervising Space

One abandonment encourages another, and all encourage crime

prob 3 one crime leads to another direct burglary multiplier model
Prob. 3: One crime leads to another – Direct burglary multiplier model

The sequence:

  • a burglary occurs, property is taken.
  • the burglar sells these stolen goods,
  • to someone who knowingly buys them
  • who re-sells these stolen goodscontinued>
prob 3 cont the accounting
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


prob 4 easy needle policy
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.
prob 4 cont disaggregate
Prob. 4, cont: Disaggregate

Disaggregate The Population Of Drug Abusers

T t = Total drug abuse population in year t

N t = New local drug abuse population in year t

Mt= Deaths of local drug abuse population in year t

Dt= Desisting local drug abuse population in year t

I t = In-migration of drug abusers to local area in year t

Ot= Out-migration of drug abusers from local area in year t

prob 4 cont basic equation
Prob 4, Cont: Basic Equation

(a) T t = T t-1 + N t - M t - D t + I t - O t


(b) T t = (T t-1 + N t + I t) - (M t + D t + O t )

prob 4 explained
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.

thanks to those who lasted marcus felson felson@andromeda rutgers edu
Thanks to those who lastedMarcus