Hotspot Analysis

Imagine a map of your city with a red dot for every crime in a year. Almost the whole map would stay blank, and the dots would pile up in a tiny handful of addresses (a corner, a parking lot, a stretch of sidewalk), forming intense red blotches: the hot spots. Hotspot analysis starts from that stubborn fact: crime is not distributed uniformly across territory or over time, but concentrates in an extreme way in very few places and moments. And what concentrates can be located, predicted and prevented.

// OriginMinneapolis, 1989: when crime went on the map

In 1989, Lawrence Sherman and his colleagues analyzed one year of 911 calls in Minneapolis: 323,000 calls. When they mapped them, they found that barely 3% of the addresses in the city generated 50% of all the calls to the police. Whole neighborhoods made not a single urgent call all year, while one particular bar or building accumulated dozens. Sherman coined the expression hot spots of crime and drew the conclusion: if crime concentrates in so few places, patrolling the whole city equally is a waste, and resources must be concentrated on the hot spots.

With David Weisburd, Sherman put the idea to the test in the Minneapolis Hot Spots Experiment (1995): of 110 hot spots, half were randomly assigned intensive police patrol and the other half normal patrol. In the spots with concentrated police presence, crimes and disorder dropped measurably. Thus was born hot spots policing, one of the few police strategies that, repeated in dozens of cities and subjected to rigorous reviews, has shown that it works without merely displacing crime to the next corner over.

// Why it concentratesWhat turns a place into a hot spot

The obvious question is why: what is it about a corner that attracts crime while the one across the street stays quiet? Here hotspot analysis connects with routine activity theory (Cohen and Felson) and with its family, environmental criminology: a hot spot arises where a motivated offender, an attractive target and the absence of a capable guardian habitually coincide. A nightclub gathers uninhibited people, money and little surveillance; a poorly lit parking lot offers targets and no gaze to deter. Criminologists distinguish crime "generators" (places that draw many people for other reasons, and with them opportunities) from "attractors" (places the offender seeks out because they know they offer easy prey).

If the problem is in the place, the solution can be there too: changing the lighting, regulating a troublesome venue or modifying the flow of people can "cool down" a hot spot without arresting anyone. This is the logic of situational prevention.

// In fictionCorners, a building and a pub where crime takes root

The best street stories are not about a predator wandering the city, but about places that produce crime night after night, whoever is in charge. In The Wire, — runs the public housing towers and the West Baltimore corners where heroin is sold: his business is a map of selling points that must be kept open. When the towers are demolished at the start of the third season, the organization goes out to fight for corners, because the market needs a fixed spot where the buyer knows he will find the seller. Marlo, who takes them from him, illustrates the other half of Weisburd's law, stability: killing or jailing whoever runs a corner does not cool it down, because the corner produces another one the next day. The same season takes the idea to the extreme with "Hamsterdam", the zones where Major Colvin tolerates drug dealing: by concentrating the market in a few empty blocks, crime in the rest of his district falls.

el rey del crack takes the selling point to its purest form: in New Jack City he seizes an entire building in Harlem, throws out the residents and turns it into a crack fortress, a single address that concentrates the business of a whole neighborhood. Zé shows how the map is built: in City of God he takes over almost every drug-selling point in the favela at gunpoint, until only his rival Carrot's is left; places are not created, they are conquered. And Begbie is a reminder that not every hot spot is a market: in the packed pub in Trainspotting where he throws a pint glass from the upper floor and sets off a brawl, alcohol, crowds, friction and no one keeping order come together, which is what turns a bar into a crime "generator". Why a few bars concentrate almost all the violence of their category is the subject of risky facilities.

AB

The Wire · Series

Avon Barksdale

MS

The Wire · Series

Marlo Stanfield

NB

New Jack City · Film

Nino Brown

ZP

City of God · Film

Zé Pequeño

FB

Trainspotting · Film

Francis Begbie

From the corners of Baltimore to a packed pub: five places where crime repeats itself. Tap to open their case file.

// The scaleMicro-places: the corner, not the neighborhood or the predator

The most counterintuitive contribution of hotspot analysis is its scale. Mapped address by address, the "bad neighborhood" breaks up into calm streets and burning segments: it is often a handful of hot corners surrounded by normal streets. The theory does not compete with neighborhood-level explanations such as social disorganization; it works one level below and asks why this doorway and not the one fifty meters away.

It also matters what kind of crime it explains. Hot spots are measured with high-volume crime: robberies, assaults, burglaries, street drug dealing, disorder, the calls that come in every week from the same address. Series by a single offender, such as those of serial killers, belong to crime pattern theory and geographic profiling, which read the locations of a series to estimate where its author lives.

// The crackThe risk of watching places and stigmatizing people

For all its empirical support, the theory has serious cracks. The first is displacement: if you concentrate the police on one corner, doesn't crime simply move to the next one? Research shows that total displacement is rare and that the opposite often happens, a "diffusion of benefits" that also cools the neighboring zones; even so, the risk forces intervention on the causes of the hot spot, not just scaring off the symptom. The second is more delicate: concentrated surveillance can turn into harassment of the communities living at those spots, almost always the poorest, feeding a cycle of over-policing, distrust and criminalization of entire neighborhoods.

The third is statistical. If the police patrol a place more, they detect more crime there, which "confirms" that it is a hot spot and justifies patrolling it even more: the data can become a self-fulfilling prophecy, especially when it feeds "predictive policing" algorithms. The vaccine lies in Weisburd's own lesson: the focus belongs on places and their conditions, not on the people who inhabit them. Using the crime map to improve environments prevents; using it to mark populations stigmatizes.

// Why it mattersVery little space, almost all the crime

Hotspot analysis shifted criminology's question: from the eternal "who offends?" to the fertile "where is crime committed, and why right there?". Reducing crime does not always require transforming people; sometimes it is enough to transform a few places. That makes crime manageable: if 5% of the territory produces 50% of the crime, a surgical intervention on that 5% can achieve what patrolling the whole city equally never could.