John E Eck

Background: Numerous studies have established that crime is highly concentrated among a small group of offenders. These findings have guided the development of various crime prevention strategies. The underlying theme of these strategies is that by focusing on the few offenders who are responsible for most of the crime, we can prevent the greatest amount of crime with the fewest resources. Nevertheless, there has been no systematic review of the many studies, so it is possible that the accepted understanding among researchers and practitioners is based on a few prominent studies that are misleading. Further, we do not know how concentrated crime is among offenders, given the variety of ways researchers report their findings. This paper systematically reviews this literature and uses meta-analysis to determine how confident we can be that crime is concentrated among a few offenders.

Methods: We first systematically reviewed the literature and found 73 studies on the concentration of crime among offenders. From those studies, we identified 15 studies on the prevalence of offending and 27 studies on the frequency of offending that provided data suitable for analysis. We then performed a meta-analysis of those studies to examine how crime is concentrated among the worst offenders and how that concentration varies between different types of offenders.

Results: We found that crime is highly concentrated in the population and across different types of offenders. Little variation in concentration exists between youths and adults or between American offenders and those from other countries. We found more variation between males and females in the concentration of offending, though we believe this may be due to the more limited data on female offenders.

Conclusions: The systematic review and meta-analysis we present here is the first study of its kind on offending concentration. This is an important step in closing this gap in the crime prevention literature, but we encourage making updates to this systematic review as new literature becomes available, and using alternate methods of summarizing these studies that could challenge these findings.

Background: Considerable research shows that crime is concentrated among a few victims. However, no one has systematically compared these studies to determine the level of concentration and its variation across studies. To address this void in our knowledge of repeat victimization, we conducted a systematic review and meta-analysis of the evidence that crime is concentrated among victims.

Methods: We distinguished between studies of victimization prevalence, which examine both victims and non-victims, and studies of victimization frequency, which only examine subjects that were victimized once or more. We identified 20 prevalence studies and 20 frequency studies that provided quantitative information sufficient for analysis. We organized data using visual binning and fitted logarithmic curves to the median values of the bins.

Results: We found that crime is concentrated within a small proportion of the subjects in both the prevalence studies and frequency studies, but also that it is more concentrated in the former. When we compared studies of business victimization to studies of household victimization, we found that victimization is more concentrated among households than among businesses in prevalence studies, but that the reverse is true for frequency studies. A comparison between personal and property victimizations shows that the patterns of re-victimizations are similar. Crime is more concentrated in the United States compared to the United Kingdom in prevalence studies, but the opposite is true when frequency studies are examined. Finally, the concentration of victimization changes over time for both the US and the UK, but the nature of that change depends on whether one is examining prevalence or frequency studies.

Conclusions: Not surprisingly, our systemic review supports the notion that a large proportion of victimizations are of a relatively small portion of the population and of a small portion of all those victimized at least once. There is no question that crime is concentrated among a few victims. However, there is also variation in concentration that we also explored.

Background: That crime is concentrated at a few places is well established by over 44 studies. This is true whether one examines addresses or street segments. Additionally, crime is concentrated among offenders and victims. Many physical, biological, and social phenomena are concentrated as well. This raises a question: is crime more or less concentrated at places than other phenomena? If it is not, then crime concentration maybe the result of standard ubiquitous processes that operate in nature. If crime is more or is less concentrated than other phenomena, then researchers need to ask why.

Methods: We synthesize results from three systematic reviews and review other literatures to provide preliminary answers.

Results: We find that although crime is more concentrated at addresses than other spatial units, this is due to the fact that more addresses have no crime than is true of larger units. When only places with one or more crimes are examined, place crime is no more concentrated than other spatial unit crime. Crime appears to be concentrated at places at about the same level as it is concentrated among offenders or victims. And crime concentration does not appear to be peculiarly concentrated compared to non-crime related phenomena.

Conclusions: The concentration of crime at places is unexceptional, and should be treated as one manifestation of a general tendency of things to be concentrated.

Background: Despite the increasing awareness and interests about the importance of crime concentration at places, scholars have not comprehensively synthesized the body of evidence related to this thesis. We conduct a systematic review and meta-analysis of the evidence that crime is concentrated among places.

Methods: We identified 44 studies that empirically examined crime concentration at place and provided quantitative information sufficient for analysis. We organized data using visual binning and fitted logarithmic curves to the median values of the bins. We examine concentration in two conditions: when all places are studied (prevalence), and when only places with at least one crime are studied (frequency).

Results: We find that crime is concentrated at a relatively few places in both conditions. We also compared concentration for calls for services to reported crime incidents. Calls for services appear more concentrated than crime at places. Because there are several ways place is defined, we compared different units of analysis. Crime is more concentrated at addresses than other units, including street segments. We compared crime concentration over time and found less concentration in 2000s compared to 1980s and 1990s. We also compared crime concentration between U.S. and non-U.S. countries and found more concentration in U.S. Finally, violent crime is more concentrated than property crime.

Conclusions: Though we systematically reviewed a comprehensive list of studies, summarizing this literature is problematic. Not only should more systematic reviews be conducted as more research becomes available, but future inquiries should examine other ways of summarizing these studies that could challenge our findings.

Objectives
We describe and explain how the findings from non-experimental studies of
the relationship between police force size and crime have changed over time.
Methods
We conduct a systematic review of 62 studies and 229 findings of police force
size and crime, from 1971 through 2013. Only studies of U.S. policing and containing
standard errors of estimates were included. Using the robust variance estimation
technique for meta-analysis, we show the history of study findings and effect sizes.
We look at the influence of statistical methods and units of analysis, and time period of
studies’ data, as well as variation in police force size over time.
Results
Findings vary considerably over time. However, compared to research standards
and in comparison to effect sizes calculated for police practices in other metaanalyses,
the overall effect size for police force size on crime is negative, small, and
not statistically significant. Changes in research methods and units of analysis cannot
account for fluctuations in findings. Finally, there is extremely little variation in police
force size per capita over time, making it difficult to estimate the relationship with
reliability.
Conclusions
This line of research has exhausted its utility. Changing policing strategy
is likely to have a greater impact on crime than adding more police.

Crime is concentrated in many ways, but three dimensions have received particular attention: place, offender, and victim (POV). In 1989, Spelman and Eck published an article in the most obscure periodical imaginable (Public Affairs Comment), comparing the three distributions. The distributions had the same shape, but place seemed more concentrated than offender, and offender more concentrated than victim. No one has bothered to make a comparison since, despite the growth in place and victim concentration research, so we do not know if these conclusions are valid. We break this quarter century of silence by reporting on a tripartite systematic review of the POV concentration literature. From this literature we derive three general distributions and offer some comments on what this literature shows (and does not). We also offer some comments on differences in how researchers approach these three distributions that make comparison difficult.

The relationship between police force size and crime control effectiveness has long been a matter of intellectual curiosity in criminology and crime prevention. Indeed, scholars and practitioners have had conflicting perspectives for more than four decades as to whether crime deterrence can be achieved by increasing police strength. If all of these findings are not a methodological artifact, we should anticipate a reasonable amount of convergence across previous studies. In this paper we report a systematic review of studies that examine the police force size–crime relationship, and assess the relevance of this literature to research and practice.

Theory and practice point to the link between place manage- ment and the likelihood of drug dealing and criminal behavior at places. Theory suggests that drug dealers select places that have weak man- agement. In an experiment conducted in San Diego, CA, 121 rental properties that had already been the target of drug enforcement were randomly assigned to two approximately equal-size treatment groups, or to a control group that received no further police actions. One treatment group received a letter from the police describing the enforcement and offering assistance; the other met with a narcotics detective under threat of nuisance abatement. Results show more evictions of drug of- fenders for both treatment groups relative to the control group, but more evictions for the meeting group than the letter group. Property owners in the meeting group also had a sizeable reduction in reported crime within six months of the intervention. There is also some evidence in support of a crime reduc...

Crime is concentrated in many ways, but three dimensions have received particular attention: place, offender, and victim (POV). In 1989, Spelman and Eck published an article in the most obscure periodical imaginable (Public Affairs Comment), comparing the three distributions. The distributions had the same shape, but place seemed more concentrated than offender, and offender more concentrated than victim. No one has bothered to make a comparison since, despite the growth in place and victim concentration research, so we do not know if these conclusions are valid. We break this quarter century of silence by reporting on a tripartite systematic review of the POV concentration literature. From this literature we derive three general distributions and offer some comments on what this literature shows (and does not). We also offer some comments on differences in how researchers approach these three distributions that make comparison difficult.

We examine the distribution of crime across street segments in Cincinnati (proximal places), and then proceed to look at the distribution of crime at addresses (proprietary places) within the segments. We find that for a substantial proportion of the proximal places, crime is concentrated at a few proprietary places. This indicates that the address is potentially implicated in the cause of crime events. Theoretical and practical implications follow.