Measuring Crime Concentration Across Cities of Varying Sizes: Complications Based on the Spatial and Temporal Scale Employed

Objectives

We argue that assessing the level of crime concentration across cities has four challenges: (1) how much variability should we expect to observe; (2) whether concentration should be measured across different types of macro units of different sizes; (3) a statistical challenge for measuring crime concentration; (4) the temporal assumption employed when measuring high crime locations.

Methods

We use data for 42 cities in southern California with at least 40,000 population to assess the level of crime concentration in them for five different Part 1 crimes and total Part 1 crimes over 2005–2012. We demonstrate that the traditional measure of crime concentration is confounded by crimes that may simply spatially locate due to random chance. We also use two measures employing different temporal assumptions: a historically adjusted crime concentration measure, and a temporally adjusted crime concentration measure (a novel approximate solution that is simple for researchers to implement).

Results

There is much variability in crime concentration over cities in the top 5 % of street segments. The standard deviation across cities over years for the temporally adjusted crime concentration measure is between 10 and 20 % across crime types (with the average range typically being about 15–90 %). The historically adjusted concentration has similar variability and typically ranges from about 35 to 100 %.

Conclusions

The study provides evidence of variability in the level of crime concentration across cities, but also raises important questions about the temporal scale when measuring this concentration. The results open an exciting new area of research exploring why levels of crime concentration may vary over cities? Either micro- or macro- theories may help researchers in exploring this new direction.

     

The Trajectories of Crime at Places: Understanding the Patterns of Disaggregated Crime Types

Objectives

Investigate the spatial concentrations and the stability of trajectories for disaggregated crime types on street segments and intersections in Vancouver, Canada.

Methods

A longitudinal analysis of 16 years of crime data using street segments and intersections as the units of analysis. We use the k-means non-parametric cluster analysis technique considering eight crime types: assault, burglary, robbery, theft, theft of vehicle, theft from vehicle, other, and total crime.

Results

The overall results for the individual crime types versus overall crime are similar: crime is highly concentrated regardless of crime type, most street segment and intersection trajectories are stable over time with the others decreasing, and most decreasing trajectories are in the same general areas. However, there are notable differences across crime types that need to be considered when attempting to understand spatial pattern changes and implement crime prevention initiatives.

Conclusions

The law of crime concentration at places holds in Vancouver, Canada for disaggregated crime types in the context of spatial concentrations and their stability over time. However, notable differences exist across crime types that should be accounted for when developing theory or policy.

     

Testing the “Law of Crime Concentration at Place” in a Suburban Setting: Implications for Research and Practice

Objective

To assess whether the “law of crime concentration at place” applies in a non-urban context. We test whether longitudinal trends in crime concentration, stability, and variability apply in a suburban setting.

Methods

We use group-based trajectory analysis to examine trends in recorded crime incidents on street segments in Brooklyn Park, a suburban city outside Minneapolis, Minnesota, over a 15-year period from 2000 to 2014.

Results

Consistent with the law of crime concentration at place, crime in Brooklyn Park is highly concentrated at a small percentage of micro-places. Two percent of street segments produced 50 % of the crime over the study period and 0.4 % of segments produced 25 % of the crime. The patterns of concentration are highly stable over time. However, the concentration of crime is substantially higher and there is much less street-by-street variability in Brooklyn Park compared to urban areas.

Conclusions

We find strong support for the application of the law of crime concentration at place to a non-urban setting, suggesting that place-based policing approaches tested in cities can also be applied to suburbs. However, there are also important differences in the concentration and variability of crime hot spots in suburbs that require further examination. Our study is based on a single setting that may not be representative of other suburban and rural areas. Finally, the clustering of hot spots raises questions about the use of street segments to analyze crime at suburban micro-places.

     

Measuring the Spatial and Temporal Patterns of Police Proactivity

Objectives

To measure where officers engage in proactive, self-initiated activities, how much time they spend being proactive, and whether their proactive activities coincide with crime patterns.

Methods

This study uses Andresen’s Spatial Point Pattern Test to compare the spatial similarity between police proactivity and crime, as well as regression modeling to explore the relationship between proactivity and crime and the time spent on proactivity and crime.

Results

In the jurisdiction examined, high levels of proactivity are noted. This proactive activity is more likely to occur in places where crime is most concentrated. Additionally, the number of proactive calls and the proactive time spent per crime-and-disorder call remain high and stable across spatial scales. For each crime call received at a street block, police initiated 0.7 proactive activities and spent approximately 28 min carrying out proactive works.

Conclusions

This study develops a way of measuring proactive activity by patrol officers using calls for service data. We find that not only do officers in this jurisdiction exhibit higher levels of proactivity to prevent crime (compared to reacting to crime), but they also do so in targeted, micro-place ways. Agencies may consider using similar techniques to gauge the levels of proactivity in their agencies if proactive activity is a goal.

     

More Places than Crimes: Implications for Evaluating the Law of Crime Concentration at Place

Objectives

The crime and place literature lacks a standard methodology for measuring and reporting crime concentration. We suggest that crime concentration be reported with the Lorenz curve and summarized with the Gini coefficient, and we propose generalized versions of the Lorenz curve and the Gini coefficient to correct for bias when crime data are sparse (i.e., fewer crimes than places).

Methods

The proposed generalizations are based on the principle that the observed crime concentration should not be compared with perfect equality, but with maximal equality given the data. The generalizations asymptotically approach the original Lorenz curve and the original Gini coefficient as the number of crimes approaches the number of spatial units.

Results

Using geocoded crime data on two types of crime in the city of The Hague, we show the differences between the original Lorenz curve and Gini coefficient and the generalized versions. We demonstrate that the generalizations provide a better representation of crime concentration in situations of sparse crime data, and that they improve comparisons of crime concentration if they are sparse.

Conclusions

Researchers are advised to use the generalized versions of the Lorenz curve and the Gini coefficient when reporting and summarizing crime concentration at places. When places outnumber crimes, the generalized versions better represent the underlying processes of crime concentration than the original versions. The generalized Lorenz curve, the Gini coefficient and its variance are easy to compute.

     

Acquisitive Crime and Inflation in the United States: 1960–2012

Objectives

Inflation is conspicuous by its absence from recent research on crime and the economy. We argue that price inflation increases the rate of crimes committed for monetary gain by fueling demand for cheap stolen goods.

Methods

The study includes inflation along with indicators of unemployment, GDP, income, consumer sentiment, and controls in error correction models of acquisitive crime covering the period from 1960 to 2012. Both short- and long-run effects of the predictors are estimated.

Results

Among the economic indicators, only inflation has consistent and robust short- and long-run effects on year-over-year change in the offense types under consideration. Low inflation helps to explain why acquisitive crime did not increase during the 2008–2009 recession. Imprisonment rates also have robust long-run effects on change in acquisitive crime rates.

Conclusions

Incorporating inflation into studies of crime and the economy can help to reduce the theoretical and empirical uncertainty that has long characterized this important research area in criminology.

     

Using Space–Time Analysis to Evaluate Criminal Justice Programs: An Application to Stop-Question-Frisk Practices

Objectives

Effects of place-based criminal justice interventions extend across both space and time, yet methodological approaches for evaluating these programs often do not accommodate the spatiotemporal dimension of the data. This paper presents an example of a bivariate spatiotemporal Ripley’s K-function, which is increasingly employed in the field of epidemiology to analyze spatiotemporal event data. Advantages of this technique over the adapted Knox test are discussed.

Methods

The study relies on x–y coordinates of the exact locations of stop-question-frisk (SQF) and crime incident events in New York City to assess the deterrent effect of SQFs on crime across space at a daily level.

Results

The findings suggest that SQFs produce a modest reduction in crime, which extends over a three-day period. Diffusion of benefits is observed within 300 feet from the location of the SQF, but these effects decay as distance from the SQF increases.

Conclusions

A bivariate spatiotemporal Ripley’s K-function is a promising approach to evaluating place-based crime prevention interventions, and may serve as a useful tool to guide program development and implementation in criminology.

     

Immigration and Crime in the New Destinations, 2000–2007: A Test of the Disorganizing Effect of Migration

Objectives

Drawing from a social disorganization perspective, this research addresses the effect of immigration on crime within new destinations—places that have experienced significant recent growth in immigration over the last two decades.

Methods

Fixed effects regression analyses are run on a sample of n = 1252 places, including 194 new destinations, for the change in crime from 2000 to the 2005–2007 period. Data are drawn from the 2000 Decennial Census, 2005–2007 American Community Survey, and the Uniform Crime Reports. Places included in the sample had a minimum population of 20,000 as of the 2005-07 ACS. New destinations are defined as places where the foreign-born have increased by 150 % or more since 1990 and with a minimum foreign-born population of 1000 in 2007.

Results

Results indicate new destinations experienced greater declines in crime, relative to the rest of the sample. Moreover, new destinations with greater increases in foreign-born experienced greater declines in their rates of crime. Additional predictors of change in crime include change in socioeconomic disadvantage, the adult-child ratio, and population size.

Conclusions

Results fail to support a disorganization view of the effect of immigration on crime in new destinations and are more in line with the emerging community resource perspective. Limitations and suggestions for future directions are discussed.

     

Does Eligibility for Tertiary Education Affect Crime Rates? Quasi-Experimental Evidence

Objectives

This paper estimates the effect of tertiary education eligibility on crime in Sweden. The hypothesis tested is that continuing to higher education decreases crime rates since it allows young people to escape inactivity and idleness, which are known to trigger crime. However, to qualify for tertiary education, individuals have to meet the eligibility requirements in upper-secondary school. Tertiary education eligibility may therefore affect crime rates.

Methods

This paper uses a panel data set of 287 Swedish municipalities over the period 1998–2010 to estimate the tertiary education eligibility effect on crime. However, estimating educational effects on crime is challenging, because investment in education is an endogenous decision. In Sweden, substantial grade inflation, increased tertiary education eligibility by more than 6% points between 1998 and 2003. Thus, since the eligibility increase is exogenous to the educational achievements of a student cohort, i.e. not accompanied by a corresponding knowledge increase, we can use the increase to identify the effect of tertiary education eligibility on crime.

Results

It is found that increasing the tertiary education eligibility rate decreases both property and violent crime substantially.

Conclusions

The results show that when young people have the opportunity to attend tertiary education, and thus escape unemployment or inactivity, their propensity to commit crime decreases.

     

The Law of Crime Concentration: An Application and Recommendations for Future Research

Objective

We address four outstanding empirical questions related to the “law of crime concentration” (Weisburd in Criminology 53:133–157, 2015): (1) Is the spatial concentration of crime stable over time? (2) Do the same places consistently rank among those with the highest crime counts? (3) How much crime concentration would be observed if crimes were distributed randomly over place? (4) To what degree does the spatial concentration of crime depend on places that are crime free?

Methods

The data are annual counts of violent and property crimes in St. Louis between 2000 and 2014. Temporal stability in the spatial inequality of crime is measured by computing the fraction of crimes that occur in the 5% of street segments with the highest crime frequencies each year. The spatial mobility of crime is measured by computing the number of years each street segment appears in the top 5% of street segments. Poisson simulations are used to estimate the fraction of crimes that could appear in the top 5% of street segments on the basis of chance alone. The impact of crime-free locales on the spatial concentration of crime is evaluated by comparing results from analyses that include and exclude crime-free street segments from the crime distributions.

Results

The concentration of crime is highly unequal and stable over time. The specific street segments with the highest crime frequencies, however, change over time. Nontrivial fractions of street segments may appear among the 5% with the highest crime frequencies on the basis of chance. Spatial concentration of crime is reduced when crime-free street segments are excluded from the crime distributions.

Conclusions

The law of crime concentration is not a measurement artifact. Its substantive significance, however, should be assessed in future longitudinal research that replicates the current study across diverse social settings.

     

Dissecting the Prevalence and Incidence of Offending During the Crime Drop of the 1990s

Objectives

To evaluate whether the 1990s crime drop reflects a decrease in offending prevalence (the fraction of the population engaged in crime), offending incidence (the frequency of offending among active criminals), or some combination of the two.

Methods

We use individual-level longitudinal data on adolescent offending patterns from the Pittsburgh Youth study (PYS), integrating information from the youngest and oldest cohorts to compare offending among 17–18 year old males at the beginning and end of the 1990s. Logistic and negative binomial regression models are estimated to assess whether there are significant differences in offending prevalence and incidence during the 1990s.

Results

The reduction in property crime rates in the PYS sample during the 1990s can be attributed to declines in both offending prevalence and incidence. The overall decline in serious violence during the 1990s for the full sample was primarily the result of a falloff in prevalence. However, for black youth our results indicate significant reductions in both the prevalence and incidence of serious violence. We did not detect a significant difference in illegal drug sales during the period.

Conclusions

Using longitudinal data on individuals to decompose aggregate crime trends into changes in the prevalence and incidence of offending offers insights into the nature of the 1990s crime drop that cannot be discerned from aggregate crime data. Future research should build on the current study by examining the specific mechanisms that influence change over time in crime prevalence, incidence, or both.

     

The Structure of Citizen Perceptions of Crime and Disorder: New Insights from a Caribbean Community

Objectives

This study builds on existing research from US cities on the construct and discriminant validity of perceptual measures of crime and disorder. It seeks to determine whether citizens distinguish between crime and disorder.

Methods

This study draws on quantitative and qualitative data from a high-crime community in Trinidad and Tobago, a small-island developing nation in the eastern Caribbean. Analysis of the quantitative data relies on exploratory and confirmatory factor analysis methods designed for use with categorical observed variables and continuous latent variables.

Results

In contrast to previous research, we find that citizens do distinguish between physical disorder and general crime, but there is a perceptual overlap for some drug-related offenses and types of social disorder.

Conclusions

This study raises questions about the external validity of research on the relationship between perceptions of crime and disorder conducted in the US, and contributes to ongoing discussions and debates about the meaning of disorder. The findings suggest the need for theory and research to explain how context shapes not only the magnitudes of these perceptions, but also their structures. The results also demonstrate the benefits of mixed-methods research approaches in this area of study.

     

Violence in Urban Neighborhoods: A Longitudinal Study of Collective Efficacy and Violent Crime

Objectives

Cross-sectional studies consistently find that neighborhoods with higher levels of collective efficacy experience fewer social problems. Particularly robust is the relationship between collective efficacy and violent crime, which holds regardless of the socio-structural conditions of neighborhoods. Yet due to the limited availability of neighborhood panel data, the temporal relationship between neighborhood structure, collective efficacy and crime is less well understood.

Methods

In this paper, we provide an empirical test of the collective efficacy-crime association over time by bringing together multiple waves of survey and census data and counts of violent crime incident data collected across 148 neighborhoods in Brisbane, Australia. Utilizing three different longitudinal models that make different assumptions about the temporal nature of these relationships, we examine the reciprocal relationships between neighborhood features and collective efficacy with violent crime. We also consider the spatial embeddedness of these neighborhood characteristics and their association with collective efficacy and the concentration of violence longitudinally.

Results

Notably, our findings reveal no direct relationship between collective efficacy and violent crime over time. However, we find a strong reciprocal relationship between collective efficacy and disadvantage and between disadvantage and violence, indicating an indirect relationship between collective efficacy and violence.

Conclusions

The null direct effects for collective efficacy on crime in a longitudinal design suggest that this relationship may not be as straightforward as presumed in the literature. More longitudinal research is needed to understand the dynamics of disadvantage, collective efficacy, and violence in neighborhoods.

     

Crimes by Visitors Versus Crimes by Residents: The Influence of Visitor Inflows

Objectives

To disaggregate the crime impact of visitor inflows. There is increasing evidence that visitors can make a major contribution to levels of crime in a given neighbourhood: crimes by visiting offenders may add to those committed by local offenders, while visitors (and their property) may provide local offenders with additional opportunities for crime.

Methods

Using police-recorded crime data for a large Eastern Canadian city we determined whether individuals charged or chargeable for property and violent crimes were visitors or residents of census tracts (CT) where crimes had been committed. This information was combined with data from a large transportation survey, allowing us to estimate daily population flows into each CT for four purposes (work, shopping, recreation, and education). Negative binomial regression models including spatial lags were used.

Results

An increase in visitor inflow not only increases the number of visitors charged with crimes but also the number of local residents charged. These effects vary significantly by visit purpose: more infractions are committed in tracts where visits are for recreation and, to a lesser extent, for shopping. Findings for work and education are mixed.

Conclusions

One important implication of our results is that, because most studies of aggregate crime counts or rates fail to account for whether crimes have been committed by visitors or residents, previous research may have provided hasty, partial, or even erroneous explanations for crime concentrations.

     

The Murder Mystery: Police Effectiveness and Homicide

Objective

Previous aggregate analyses of the effect of police on crime show that increases in police staffing are especially effective at preventing homicide. This conflicts with evidence that suggests standard police methods should be more effective at preventing robbery, auto theft, and other property crimes. My objective is to reconcile the two.

Methods

Regression of crime rates on uniformed police staffing and other economic and demographic covariates, for a panel of 59 US cities for the period 1970–2013.

Results

Lagged crime rates are strong and statistically significant predictors of both policing staffing and crime rates, particularly homicide. When lags are included in the specification, the apparent effect of police on homicide drops by more than 70 %; there is little change in the effect of police on other crimes. Findings are robust with respect to specification and method.

Conclusions

Previous studies omitted lags and overstated the effectiveness of police on homicide. Because murder accounts for almost 40 % of all costs of crime in US cities, it is no longer clear whether increasing police force size is a cost-effective way to cut crime. Improving police tactics is more likely to work and less expensive.

     

The efficacy of foot patrol in violent places

Objectives

This study examines the effectiveness of foot patrol in violent micro-places. A large urban police department deployed foot patrol in micro-places (hot spots) for a period of 90 days for two shifts each day. Our objective is to determine whether this activity impacted violent crime in these hot spots and whether spatial displacement of crime occurred.

Methods

Eight eligible foot beat locations were set by examining crime rates for previous years in order to identify micro-places of high criminal activity. We employed a quasi-experimental design comparing the four treatment to the four control areas, estimating panel-specific autoregressive models for 30 weeks prior to and 40 weeks after the treatment.

Results

Time series models revealed statistically significant reductions in violent crime in the micro-places receiving foot patrol treatment, while no such reductions were observed in the control areas. The deterrent effect, however, was short and dissipated quickly. Control areas did not experience any crime prevention benefit during this time period. No evidence of crime displacement to spatially contiguous areas was detected.

Conclusions

This contributes to the growing body of knowledge that focused police strategies within hot spots impact violent crime. Specifically, the implementation of foot patrol in high crime hot spots led to measurable reductions in aggravated assaults and robberies, without displacing crime to contiguous areas.

     

The Concentration and Stability of Drug Activity in Seattle,Washington Using Police and Emergency Medical Services Data

Objectives

Prior research demonstrates that crime is highly concentrated at place and that these concentrations are stable from year to year, highlighting the importance of place to crime control and prevention. A potential limitation is that most studies only use one data source to diagnose these patterns. The present study uses data from both police and emergency medical services (EMS) to explore the spatial concentration and stability of drug activity in Seattle, Washington from 2009 to 2014.

Methods

We use concentration graphs and group-based trajectory analysis to examine concentration and stability of calls related to drug activity in both data sources separately and combined. Additionally, we employ Andresen’s S-Index to determine the similarity of concentration within the SPD data, the EMS data and the combined data year to year as well as the degree of co-location between the SPD and EMS data during the study period.

Results

We find a high degree of concentration and group-based stability for both SPD and EMS drug calls across all street segments in Seattle. Conversely, we find only moderate local geographic stability of drug use across street segments as indicated by each of the data sources over the study period. Last, we find the spatial patterns in drug use as indicated by each data source are significantly different each year.

Conclusions

At the same time these findings provide support for the law of crime concentration, they also raise questions about local stability patterns. Additionally, they highlight the importance of expanding inquiries of crime and place research into new data sources. Our results serve to reinforce the importance of multiple data sets in quantifying, understanding, and responding to the drug problem in Seattle.

     

The Role of Immigration: Race/Ethnicity and San Diego Homicides Since 1970

Objectives

The temporal variation in homicide is examined by studying trends in race/ethnic specific killings (e.g. Blacks, Latinos and Whites). Two substantively important issues are also addressed—a closer examination of the role community heterogeneity plays in homicide levels and the treatment of immigration as an endogenous social process.

Methods

Data are reported homicides in the city of San Diego, California over the period 1960–2010. The address of each killing is geocoded into 341 census tracts.

Results

We find that neighborhoods experiencing increases in the foreign-born population tend to be less violent. White and Latino homicide victimization was reduced significantly as a product of increases in the neighborhood concentration of foreign-born individuals. Supplementary analyses did not find empirical evidence that the influx of foreign-born individuals could (or should) be considered a disruptive social process. Over the past five decennial census periods, the exponential increase in immigration in this border city is not associated with an increase in homicide victimization.

Conclusions

When examined through a wider temporal lens than is typically employed, and accounting for the endogeneity of immigrant residential settlement, we find no support for the claims that immigration is a crime generating social process.

     

Do Schools Cause Crime in Neighborhoods? Evidence from the Opening of Schools in Philadelphia

Objectives

To assess the impact of schools on crime in neighborhoods.

Methods

We utilize data of charter and public schools in Philadelphia to estimate the effect of school openings on neighborhood crime patterns between 1998 and 2010. We estimate the change in crime in areas surrounding schools before and after their opening compared to areas where schools were always open with Poisson regression models. We also estimate changes in crime in census tracts as schools are added compared to census tracts that never had schools. Finally, we compare estimates from Poisson regression models to those derived from permutation tests where schools are randomly assigned different opening dates.

Results

We find no evidence that school openings increase crime relative to locations where schools were always open or never had schools. The models generally produce null effects, though there is some evidence for a reduction in property crimes for public school openings and a reduction in violent crimes for charter school openings within certain distances. Estimates at the census tract level show that changes in the number of schools are not associated with any changes in crime relative to tracts with no schools.

Conclusions

Contrary to a large theoretical and empirical literature, the results suggest that school locations play a minimal role in neighborhood crime production in Philadelphia. Future research should investigate specific contexts and mechanisms, such as land-use characteristics and travel patterns to schools, which may interact with specific school settings in ways that are related to crime production.