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Hot spots are small geographic units with high rates of activity that demand some sort of police response.2 There is no singular definition of “small units” or “high rates.” These small units can
range in size from individual addresses or buildings to single street segments (i.e., both sides of a street from intersection to intersection) to very small groups of street segments with similar policing problems, such as a drug market.3 What is important is that these geographic areas are all smaller than the geographic units that police departments typically use for dividing up patrol resources (e.g., patrol beats, zones, sectors). Hot spots are often referred to as micro places because of their small size and to differentiate them from larger geographic units such as communities, districts, and neighborhoods.
There is also no firm rule as to how much activity must be found in micro places before they can be considered to have “high rates.” This determination will vary across jurisdictions, based on the historical and overall levels of incidents. As described more in the next section, hot spots are often defined by drawing upon a rank-ordered list of the highest incident locations in the city (e.g., addresses, streets) based on calls for service or other indicators. Thus, places are not defined as hot spots by reaching an absolute threshold of activity, but instead because of very high levels of crime and disorder relative to other places in the city during a specified time period. Exactly how high will vary based on the community’s characteristics. Police should consider incident data in conjunction with departmental resources and resident concerns when selecting hot spots for intervention. A hot spot in a densely populated urban area is likely to have a much higher level of activity than a hot spot in a less densely populated suburban area, but both would represent the highest crime locations in their respective jurisdictions.†
† See Problem-Solving Tools Guide No. 13, Identifying and Defining Policing Problems, for further discussion of this topic.
Regardless of how hot spots are defined, results from many cities in the United States and around the world show that a small number of micro places are responsible for a substantial amount of total crime in a city. That is, the hottest spots of crime in a city, regardless of the specific unit of geography chosen, are responsible for a large proportion of a jurisdiction’s crime problem. About 50 percent of crime is concentrated at approximately 5 percent of the places in a city.4 These strong concentration levels remain when looking at different-sized hot spots, different data sources (e.g., calls versus incidents), and different crime types (e.g., all crime versus specific crime types).
In some cities, analysis has shown that hot spots are stable over time. A study in Seattle, Washington, that included crime incident data from 1989 to 2004 confirmed not only the concentration of crime, but also that crime hot spots tend to stay hot over long periods of time.5 Between 5 and 6 percent of street segments accounted for 50 percent of crime incidents each year, reinforcing the idea that crime is highly concentrated at a relatively small number of places.
Crime was especially stable in a small group of high-crime segments the authors refer to as the “chronic group.” The streets in this chronic group remained among the hottest in the city throughout the 16-year study period, and although they represented only 1 percent of all street segments in Seattle, they were the sites of 22 percent of crime in the city. Subsequent studies have found similar results. 6
This level of concentration and stability is also found in specific crime types. In Boston, Massachusetts, for example, just 4.8 percent of the street segments were the site of 73.9 percent of all gun assaults between 1980 and 2008. Only 3 percent of streets and intersections showed variability in levels of gun assaults over time, suggesting a great deal of stability.7 Results were similar when examining the concentration and stability of robberies over time.8
Are hot spots of crime all clustered in the same part of a city? This is important to explore, because it addresses the issue of whether it is necessary for resources to be focused on micro places for hot spot policing. For example, if all the crime hot spots were concentrated in only one or two neighborhoods in a city, then neighborhood- or beat-level initiatives might be just as effective as hot spot approaches in addressing crime concentrations.
Evidence to date suggests that crime hot spots can be found throughout a city. For example, an examination of 56 drug markets in Jersey City, New Jersey, found that although drug locations were more concentrated in socially disadvantaged areas, they were also found in areas that were generally seen as more established and better off.9 This suggested that even “good” neighborhoods can have “bad” places. Importantly, most places, even in very disadvantaged neighborhoods, were relatively free of serious drug problems.
The Seattle study mentioned earlier found that although hot spots may be more common in high-activity places like the central business district, they were also found in a variety of neighborhoods. Furthermore, neighborhoods with a higher concentration of hot spots tended to have sizable proportions of crime-free locations. There is also evidence of street-by-street variability. In other words, hot spots are often close to or even border streets with little or no crime. These findings suggest the usefulness of a crime-prevention approach that narrows the focus to high-crime street segments or micro places as opposed to larger geographic units like neighborhoods or beats. Initiatives at larger areas are less likely to use resources efficiently because crime and disorder problems are typically concentrated on only a small number of streets or addresses within a neighborhood.
Many place-based theories have been used to help explain why crime and other police problems are so highly concentrated at a small number of places. These theories generally fall into one of two categories: opportunity theories and social disorganization theories.
Opportunity theories have been the most common approach for understanding the emergence and stability of hot spots. In general, these theories focus specifically on crime problems and examine the opportunity structures of particular places or situations to explain why crime is common at some places and not others. Just as crime is not randomly distributed across cities and jurisdictions, opportunities to engage in criminal activity are also more highly concentrated in some places than others.
Routine activity theory—which argues that crime occurs when a motivated offender, a suitable target, and the lack of capable guardianship converge in space and time—has been an especially important theory for understanding hot spots.10
Suitable targets and a lack of capable guardianship create opportunities for crime. Suitable targets can be physical items (e.g., expensive merchandise) or potential victims (e.g., a person walking alone late at night) that may attract potential offenders. Capable guardianship can be provided not only by the police, but also by place managers (e.g., a landlord, a bus driver), community residents (e.g., a neighborhood watch), or physical devices (e.g., CCTV cameras). Making targets less suitable or increasing levels of guardianship are common approaches to block opportunities and reduce crime in hot spots. Police can also increase levels of guardianship through their presence alone. This can have important deterrent effects, because crime and disorder are likely to be witnessed by police.11 Rational choice theory assumes that potential offenders consider the costs and benefits before committing a criminal act, and so increasing the costs of crime—the risk of police witnessing the crime—through guardianship and reducing the benefits through opportunity blocking should help prevent crime.12
Social disorganization theories have a long history in criminology, but have typically been used to understand differences in crime at the neighborhood or community level. The focus of these theories tends to be on the social characteristics of neighborhoods that are associated with higher crime rates. These social characteristics often include economic disadvantage, racial diversity, and frequent turnover in residents.13
The concept of collective efficacy helps explain why socially disorganized neighborhoods may have more crime. Collective efficacy refers to a community’s level of social cohesion and the extent to which residents are willing to intervene to bring social control to the neighborhood.14 In other words, neighborhoods high in collective efficacy have higher levels of mutual trust among neighbors, and there is a greater shared sense of the importance of working together to keep the community safe. Components of social disorganization make it difficult for collective efficacy to develop. For example, when residential tenure is short, neighbors are less likely to know one another and thus less frequently look out for one another and the neighborhood.
This focus on informal social control is also in line with the broken windows theory.15 This theory argues that when disorderly behavior is ignored by residents and the police, over time potential offenders recognize the neighborhood as a place with low social control and allow more serious crime to move in. Based on the theory, police can play a role in disrupting this cycle through improving quality-of-life issues and dealing with disorder problems.
Although police have little control over neighborhood economic conditions, they could play a role in building collective efficacy through efforts to build relationships with and between residents. This could help increase social control and reduce crime.16
Both opportunity and social disorganization perspectives play a role in understanding why crime is highly concentrated in particular places.17 Opportunity factors seem to play an especially large role. Hot spot streets are more likely to have high numbers of residents and employees, which provide opportunities for victimization. Main roads in a city also are more likely to be crime hot spots, since these offer opportunities to easily make contact with suitable targets (and to easily leave after the criminal event). Social disorganization and broken windows factors are also influential. Streets with more physical disorder, higher levels of economic disadvantage, and lower levels of collective efficacy are more likely to be crime hot spots.