The Measure of Vice and The Measure of Vice and SinSin

A Review of the Uses, A Review of the Uses, Limitations and Implications of Limitations and Implications of

Crime DataCrime Data

Alex Tabarrok, Paul Heaton, Eric Helland

Petty’s CallPetty’s Call In 1670 William Petty, In 1670 William Petty,

founder of empirical founder of empirical economics, called for the economics, called for the collection of official collection of official statistics on “the number of statistics on “the number of people, the quality of people, the quality of inebriating liquors spent, inebriating liquors spent, the number of unmaryed the number of unmaryed persons between 15 and 55 persons between 15 and 55 years old, the number of years old, the number of Corporall sufferings and Corporall sufferings and persons imprisoned for persons imprisoned for Crime” all so that that we Crime” all so that that we might know “the measure of might know “the measure of Vice and Sin in the nation.”Vice and Sin in the nation.”

Sir William Petty(1623-1687)

Source: Bowood House

Sources of Crime DataSources of Crime Data Uniform Crime Reports (UCR)

– Supplementary Homicide ReportsSupplementary Homicide Reports– Supplementary Property ReportsSupplementary Property Reports– Law Enforcement Employees and Law Enforcement Law Enforcement Employees and Law Enforcement

Officers Killed or Assaulted (LEOKA)Officers Killed or Assaulted (LEOKA) National Incident-Based Reporting Systems (NIBRS) The National Crime Victimization Survey (NCVS) The Recidivism of Prisoners Released in 1994 Law Enforcement Management and Administrative Sta

tistics (LEMAS) International Crime Victimization Survey Geographic Crime Data: Crime Mapping and Spatial An

alysis

Uniform Crime ReportsUniform Crime Reports The UCR program began in The UCR program began in

1930 with 400 cities 1930 with 400 cities participatingparticipating

The FBI collects The FBI collects crime crime data data from from police departments or police departments or agencies.agencies. Crimes are Crimes are broken up into Part I broken up into Part I (major crimes) offenses (major crimes) offenses and Part II offenses. and Part II offenses.

Jurisdictions are not Jurisdictions are not required to participate in required to participate in the UCR program but in the UCR program but in 2007 97% of the U.S. 2007 97% of the U.S. population is covered, (FBI population is covered, (FBI UCR FAQs) albeit with UCR FAQs) albeit with reporting breaks and reporting breaks and errors at the agency level.errors at the agency level.

Part IPart I Part II Part II (sample)(sample)

Violent:Violent:

MurderMurder

Forcible Forcible RapeRape

RobberyRobbery

Aggravated Aggravated AssaultAssault

Property:Property:

BurglaryBurglary

LarcenyLarceny

Motor Motor Vehicle TheftVehicle Theft

ArsonArson

Other AssaultOther Assault

Forgery Forgery

Fraud Fraud

EmbezzlementEmbezzlement

Stolen PropertyStolen Property

VandalismVandalism

Weapons (Carrying, Weapons (Carrying, Possessing)Possessing)

Prostitution/Prostitution/commercialized Vicecommercialized Vice

Other sex offensesOther sex offenses

Drug AbuseDrug Abuse

GamblingGambling

DUIDUI

Liquor LawsLiquor Laws

DrunkennessDrunkenness

Disorderly ConductDisorderly Conduct

Uniform Crime ReportsUniform Crime Reports For the For the Part One offensesPart One offenses, the UCR includes the number of , the UCR includes the number of

offenses reported as well as the number of arrests by age, sex, offenses reported as well as the number of arrests by age, sex, and race of person arrested and race of person arrested all by monthall by month. Clearance rates are also . Clearance rates are also included.included. Percent cleared is offenses cleared/total offenses. An Offense can by cleared by Percent cleared is offenses cleared/total offenses. An Offense can by cleared by

arrest or “exceptional means”, meaning they have identified the offender arrest or “exceptional means”, meaning they have identified the offender through evidence but through evidence but encountered a circumstance outside the control of law encountered a circumstance outside the control of law enforcement that prohibits the agency from arresting, charging, and prosecuting enforcement that prohibits the agency from arresting, charging, and prosecuting the offender (i.e. death of offenders or victims refusal to cooperate).the offender (i.e. death of offenders or victims refusal to cooperate).

For For Part II Offenses Part II Offenses only arrests by month (by age, sex and race) only arrests by month (by age, sex and race) are available. Agencies do not have to report Part II data and thus are available. Agencies do not have to report Part II data and thus this data is more incomplete than Part I data.this data is more incomplete than Part I data.

Supplementary Homicide ReportsSupplementary Homicide Reports add age, sex, and race of add age, sex, and race of victims and (where-known) offenders, victim-offender victims and (where-known) offenders, victim-offender relationships, weapons used, and circumstances surrounding the relationships, weapons used, and circumstances surrounding the homicides.homicides.

  Supplementary Property ReportsSupplementary Property Reports include information on the include information on the value and type of property stolen during a murder, rape, robbery, value and type of property stolen during a murder, rape, robbery, burglary, motor vehicle theft or larceny as well as basic burglary, motor vehicle theft or larceny as well as basic information about the crime (e.g. robbery is subdivided into information about the crime (e.g. robbery is subdivided into highway, common house, gas station, bank. Etc.) highway, common house, gas station, bank. Etc.)

AggregationsAggregations The atom of the UCR is the agency/month.The atom of the UCR is the agency/month. Agency data is aggregated to county, state, and national levels by Agency data is aggregated to county, state, and national levels by

the FBI and other agencies.the FBI and other agencies. The The National Archive of Criminal Justice Data (NACJD), (NACJD), a part of a part of

the the Interuniversity Consortium for Political and Social ResearchInteruniversity Consortium for Political and Social Research ((ICPSRICPSR), contains the most complete yet still relatively accessible ), contains the most complete yet still relatively accessible subset of the UCR data in electronic form.subset of the UCR data in electronic form.

The NAJCD aggregates the agency level data to the county level. The NAJCD aggregates the agency level data to the county level. County level data is very useful if one wants to examine correlates County level data is very useful if one wants to examine correlates of crime because a wide variety of demographic data is available of crime because a wide variety of demographic data is available from the Census by county.from the Census by county.

The county data includes information on Part One and Part Two The county data includes information on Part One and Part Two offenses and also arrests by under and over 18 but does not offenses and also arrests by under and over 18 but does not otherwise include age, sex, or race characteristics of offenders. otherwise include age, sex, or race characteristics of offenders.

Not all agencies report every month so the NAJCD must impute Not all agencies report every month so the NAJCD must impute missing data to aggregate to the county-level. The agencies missing data to aggregate to the county-level. The agencies imputation algorithm changed in 1994 and thus comparisons pre imputation algorithm changed in 1994 and thus comparisons pre and post-1994 have to be done with care. County level data is and post-1994 have to be done with care. County level data is available from 1977-2010 (continuing). available from 1977-2010 (continuing).

All of this data can be accessed conveniently from the NAJCD’s All of this data can be accessed conveniently from the NAJCD’s UCR Resource Guide..

Accessing the DataAccessing the Data

The first place to look is the FBI’s The first place to look is the FBI’s UCR Data Tool.. The FBI offers quick and easy access to Part One The FBI offers quick and easy access to Part One

offense rates and numbers by agency (with offense rates and numbers by agency (with population greater than 10,000) since 1985. population greater than 10,000) since 1985. Aggregated data by state or for the nation as a Aggregated data by state or for the nation as a whole are available for the years (1960-whole are available for the years (1960-continuing). A variety of other information on continuing). A variety of other information on offenses, arrests and demographics by various offenses, arrests and demographics by various aggregations, including counties, can be also aggregations, including counties, can be also found at found at The Bureau of Justice Statistics..

Accessing the DataAccessing the Data Another source for quick access to various tabulations of the Another source for quick access to various tabulations of the

UCR data including aggregations to county, state and region is UCR data including aggregations to county, state and region is FBI’s annual report FBI’s annual report Crime in the United States (1995- (1995-continuing).continuing).

A longer time-series is available through the data cubes A longer time-series is available through the data cubes application of the application of the National Consortium on Violence Research . . Simple online data analysis is also available for some series at Simple online data analysis is also available for some series at the the Office of Juvenile Justice and Delinquency Prevention . .

If the BJS has what you want then it’s probably the easiest and If the BJS has what you want then it’s probably the easiest and best place to get what you want but often the BJS data will not best place to get what you want but often the BJS data will not have enough detail, a long enough time frame, or the right have enough detail, a long enough time frame, or the right variables. For more detailed analysis, the variables. For more detailed analysis, the National Archive of Criminal Justice Data contains the most contains the most complete yet still relatively accessible subset of the UCR data complete yet still relatively accessible subset of the UCR data in electronic form.in electronic form.

Further data can be requested from the FBI UCR Further data can be requested from the FBI UCR Communications Unit.Communications Unit.

UsesUses

When aggregated to the state or When aggregated to the state or national level the basic UCR Part One national level the basic UCR Part One data on violent and property crime data on violent and property crime reports are one of the primary reports are one of the primary sources of data for understanding sources of data for understanding overall crime trends in the United overall crime trends in the United States (the other primary source States (the other primary source being the National Victimization being the National Victimization Survey to be discussed below). Survey to be discussed below).

Figure 1, for example, shows the violent and property crime indexes Figure 1, for example, shows the violent and property crime indexes from 1960-2005 based on UCR data. Between 1960 and 1980 crime from 1960-2005 based on UCR data. Between 1960 and 1980 crime rates in the United States doubled. For about ten years crime rates rates in the United States doubled. For about ten years crime rates fluctuated before beginning to fall quite dramatically in the early fluctuated before beginning to fall quite dramatically in the early 1990s. Understanding these trends is a key question for economist 1990s. Understanding these trends is a key question for economist interested in crime and criminologists (e.g. Levitt).interested in crime and criminologists (e.g. Levitt).

Property Crime Rate

Violent Crime Rate

200

03

000

400

05

000

600

0P

rope

rty

Cri

me

Ra

te

200

400

600

800

Vio

len

t Cri

me

Ra

te

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005Year

Source: FBI, Uniform Crime Reports as prepared by the National Archive of Criminal Justice Dataand available online at http://bjsdata.ojp.usdoj.gov/dataonline/Search/Crime/Crime.cfm

per 100,000 pop, 1960-2006Violent and Property Crime Rates

The peak probability of offending for both blacks and whites is around age 20 but black The peak probability of offending for both blacks and whites is around age 20 but black homicide offenders are clustered around age 20 to a greater extent than white offenders – homicide offenders are clustered around age 20 to a greater extent than white offenders – indicating, as is well known, the very high rate of offending among young black men. Victim indicating, as is well known, the very high rate of offending among young black men. Victim ages tend to follow offender ages so Figure 2 also suggests high rates of victims among ages tend to follow offender ages so Figure 2 also suggests high rates of victims among young blacks. A density function is a “sophisticated histogram.” The total area under the young blacks. A density function is a “sophisticated histogram.” The total area under the density function is equal to 1 and the area under the density function between any two density function is equal to 1 and the area under the density function between any two points is the probability that a randomly drawn observation lies between those two points. points is the probability that a randomly drawn observation lies between those two points.

Black

White

0.0

2.0

4.0

6D

ens

ity

0 20 40 60 80 100OFFENDER 1: AGE

Source: Supplementary Homicide Reports, 2004.Note: For incidents with multiple offenders the first offender's age was used.

Distribution of Homicide Offender Agesfor

Black and White Offenders, 2004

The percentage of white and black young (aged 14-24) males among the population and among The percentage of white and black young (aged 14-24) males among the population and among homicide offenders from 1976-2005. In 1989, for example, young black males committed nearly homicide offenders from 1976-2005. In 1989, for example, young black males committed nearly 26% of all homicides while accounting for just 1.2% of the population. In the same year, young 26% of all homicides while accounting for just 1.2% of the population. In the same year, young white males committed around 17% of all homicides while accounting for 7% of the population. white males committed around 17% of all homicides while accounting for 7% of the population. Thus both young black and white males committed homicides in greater proportion than expected Thus both young black and white males committed homicides in greater proportion than expected by population alone but the ratio was far higher among young, black males. Over the 1976-2005 by population alone but the ratio was far higher among young, black males. Over the 1976-2005 period the ratio of offender percentage to population percentage for young black males averaged period the ratio of offender percentage to population percentage for young black males averaged 20.7 and for young white males 2.5. Also evident in the figure is the large increase in black 20.7 and for young white males 2.5. Also evident in the figure is the large increase in black offending rates from 1985-1995 during the so-called crack epidemic (Fryer, Heaton, Levitt, Murphy offending rates from 1985-1995 during the so-called crack epidemic (Fryer, Heaton, Levitt, Murphy 2005).2005).

Black, Young-Male Offenders (%)

White, Young-Male Offenders (%)

White, Young-Male Pop. (%)

Black, Young-Male Pop. (%)

Bla

ck R

atio

Wh

ite R

atio

Avg

=20

.7

Avg

=2.

5

01

02

03

04

0

1976 1980 1985 1990 1995 2000 2005Year

Source: Bureau of Justice Statistics, Homicide Trends in the United States, 2007.Available online at http://www.ojp.usdoj.gov/bjs/homicide/homtrnd.htm#contents

White and Black Males Aged 14-24as Percentage of

Population and Homicide Offenders, 1976-2005

Problems and IssuesProblems and Issues Hierarchy ruleHierarchy rule: when a single incident involves multiple Part One offenses, : when a single incident involves multiple Part One offenses,

the agency report that crime, and only that crime which is highest on the list the agency report that crime, and only that crime which is highest on the list of Part One offenses (called the hierarchy list). The FBI’s UCR Handbook of Part One offenses (called the hierarchy list). The FBI’s UCR Handbook provides a useful example of the hierarchy rule:provides a useful example of the hierarchy rule:– SituationSituation: A burglar broke into a home, stole several items, and placed : A burglar broke into a home, stole several items, and placed

them in a car belonging to the owner of the home. The homeowner them in a car belonging to the owner of the home. The homeowner returned and surprised the thief, who in turn knocked the owner returned and surprised the thief, who in turn knocked the owner unconscious by hitting him over the head with a chair. The burglar drove unconscious by hitting him over the head with a chair. The burglar drove away in the homeowner’s car. away in the homeowner’s car.

– Applying the Hierarchy Rule: Applying the Hierarchy Rule: A Burglary—Forcible Entry (5a), A Burglary—Forcible Entry (5a), Larceny-theft (6), Robbery—Other Dangerous Weapon (3c), Aggravated Larceny-theft (6), Robbery—Other Dangerous Weapon (3c), Aggravated Assault—Other Dangerous Weapon (4d), and Motor Vehicle Theft—Auto Assault—Other Dangerous Weapon (4d), and Motor Vehicle Theft—Auto (7a) occurred in this situation. After classifying the offenses, the (7a) occurred in this situation. After classifying the offenses, the reporting agency must score only one offense—Robbery— Other reporting agency must score only one offense—Robbery— Other Dangerous Weapon (3c)—the crime appearing first in the list of Part I Dangerous Weapon (3c)—the crime appearing first in the list of Part I offenses. offenses.

The hierarchy rule applies only to single-incidents The hierarchy rule applies only to single-incidents notnot to multiple offenses to multiple offenses separated in time or place but committed by the same criminals. For separated in time or place but committed by the same criminals. For example, (again from the UCR handbook) a gunman surprises a man and a example, (again from the UCR handbook) a gunman surprises a man and a woman parked in a car. He kills the man and abducts the woman driving her woman parked in a car. He kills the man and abducts the woman driving her across town to a secluded spot where she is raped. The murder and the rape across town to a secluded spot where she is raped. The murder and the rape are separated in time and space and are considered two incidents – thus the are separated in time and space and are considered two incidents – thus the hierarchy rule would not apply and both crimes would be reported. hierarchy rule would not apply and both crimes would be reported.

Violent:Violent:

MurderMurder

Forcible Forcible RapeRape

RobberyRobbery

AggravatAggravated ed AssaultAssault

PropertyProperty::

BurglaryBurglary

LarcenyLarceny

Motor Motor Vehicle Vehicle TheftTheft

ArsonArson

Problems and Problems and IssuesIssues

The primary practical problem with UCR The primary practical problem with UCR data is that a surprising amount of it is data is that a surprising amount of it is missing or inaccurate. The national, missing or inaccurate. The national, state and county data are aggregated state and county data are aggregated using data from approximately 17 to 18 using data from approximately 17 to 18 thousand reporting agencies (typically thousand reporting agencies (typically police departments). If we think of police departments). If we think of these reporting agencies as providing these reporting agencies as providing the atoms from which all the other data the atoms from which all the other data is built then an uncertainty principle is built then an uncertainty principle applies. The closer we get to the applies. The closer we get to the atoms, the less certain things appear. atoms, the less certain things appear.

At the national level, random errors are At the national level, random errors are likely to cancel. likely to cancel.

As we disaggregate to the state level As we disaggregate to the state level then missing data becomes important. then missing data becomes important. Table X, for example, shows the states Table X, for example, shows the states and years between 1980-2005 for and years between 1980-2005 for which Supplementary Homicide which Supplementary Homicide Reports are not available or are so low Reports are not available or are so low as to require imputation.as to require imputation.

Note that it’s not just Supplementary Note that it’s not just Supplementary Reports which may be unavailable – Reports which may be unavailable – this is just an illustration of the types of this is just an illustration of the types of problems that exist in the UCR data. problems that exist in the UCR data.

Table X: States and Years in Which Supplementary Homicide Reports are Not Available or Severely

Undercounted 1980-2005

State Data years not available Alabama 1999

Delaware 1994, 1995 District of Columbia

1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005

Florida 1988, 1989, 1990, 1991, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005

Illinois 1984, 1985, 1987 Iowa 1991 Kansas 1988, 1993, 1994, 1995, 1996, 1997,

1998, 1999, 2000 Kentucky 1987, 1988, 1994, 1999, 2000, 2001,

2002, 2003 Louisiana 1991 Maine 1991, 1992, 1993 Montana 1982, 1986, 1987, 1990, 1993, 1994,

1996, 1997, 1998, 1999, 2001, 2002 Nebraska 1987, 1993, 1994, 1995, 1996, 1997,

1998, 1999, 2000, 2001, 2002, 2003, 2005

New Hampshire 1997 New Mexico 1981 North Dakota 1991 South Dakota 1997 Vermont 1981, 1982, 1983 Wisconsin 1998 Note: Severely undercounted is defined as collected at a rate such that total homicides are more than 50% below the rate predicted by the FBI.

Source: Puzzanchera, C. and Kang, W. (2008). "Easy Access to the FBI's Supplementary Homicide Reports: 1980-2005." Online. Available: http://ojjdp.ncjrs.gov/ojstatbb/ezashr/

Problems and IssuesProblems and Issues If we disaggregate further to the county level then more data is If we disaggregate further to the county level then more data is

missing and the NAJCD imputes as necessary. missing and the NAJCD imputes as necessary. Regarding the county level offense data, Maltz and Targanski Regarding the county level offense data, Maltz and Targanski

(2002, 2003) argue ‘‘that in their current condition, county-level (2002, 2003) argue ‘‘that in their current condition, county-level UCR crime statistics cannot be used for evaluating the effects of UCR crime statistics cannot be used for evaluating the effects of changes in policy.’’ Lott and Whitley 2003, offer a more optimistic changes in policy.’’ Lott and Whitley 2003, offer a more optimistic argument but recognize that account must be made of the argument but recognize that account must be made of the sometimes poor quality of the county data.sometimes poor quality of the county data.

As we disaggregate further to the atom we find plenty of missing As we disaggregate further to the atom we find plenty of missing data – Maltz (1999), for example, found that between 1992 and data – Maltz (1999), for example, found that between 1992 and 1994 only 64 percent of agencies filed reports for each of the 36 1994 only 64 percent of agencies filed reports for each of the 36 months and 19 percent filed no reports at all during this period. It months and 19 percent filed no reports at all during this period. It should also be noted that everything that has been said about the should also be noted that everything that has been said about the offense data applies to an even greater extent to the arrest data offense data applies to an even greater extent to the arrest data (Maltz 1999).(Maltz 1999).

Recently Maltz has cleaned up and flagged the Recently Maltz has cleaned up and flagged the agency data (1960-(1960-2004) for issues and problems.2004) for issues and problems.

Problems and IssuesProblems and Issues When using the agency-level data, When using the agency-level data,

especially for smaller agencies, we must especially for smaller agencies, we must bear in mind the wisdom of the British bear in mind the wisdom of the British economist Sir Josiah Stamp (1929, 258) economist Sir Josiah Stamp (1929, 258) who said:who said:

  – ““The government are very keen on amassing The government are very keen on amassing

statistics. They collect them, add them, raise statistics. They collect them, add them, raise them to the nth power, take the cube root and them to the nth power, take the cube root and prepare wonderful diagrams. But you must prepare wonderful diagrams. But you must never forget that every one of these figures never forget that every one of these figures comes in the first instance from the village comes in the first instance from the village watchman, who just puts down what he damn watchman, who just puts down what he damn pleases.”pleases.”

Uniform Crime ReportsUniform Crime ReportsProsPros ConsCons

Covers all states in the U.S. for over Covers all states in the U.S. for over 50 years50 years Uniform definitions across time and Uniform definitions across time and space – this allows for comparisons space – this allows for comparisons across locations and time.across locations and time. Ability to disaggregate the data Ability to disaggregate the data over different geographic entities over different geographic entities (agencies, cities, and states).(agencies, cities, and states). Police cannot observe and record Police cannot observe and record all all crime that takes place, however crime that takes place, however police reports are more police reports are more comprehensive than reports of comprehensive than reports of prosecutions and/or numbers of prosecutions and/or numbers of inmates in prison (not all reports lead inmates in prison (not all reports lead to arrests, not all arrests lead to to arrests, not all arrests lead to prosecutions, not all prosecutions lead prosecutions, not all prosecutions lead to jail time)to jail time)

Possibilities of political manipulation Possibilities of political manipulation of crime statisticsof crime statistics Different interpretations of Different interpretations of classifications of crime across classifications of crime across agenciesagencies Data missing from entire Data missing from entire jurisdictions is extrapolated from jurisdictions is extrapolated from jurisdictions with similar populations, jurisdictions with similar populations, could lead to sampling bias. If only a could lead to sampling bias. If only a few months of data are reported those few months of data are reported those figures are used to calculate the figures are used to calculate the statistics for the rest of that yearstatistics for the rest of that year While offenses reported are While offenses reported are conveyed in UCR for Part I crimes, conveyed in UCR for Part I crimes, only arrests are reported for Part II only arrests are reported for Part II crimes, which can be difficult to crimes, which can be difficult to analyze. analyze.

How Many Homicides in the How Many Homicides in the United States in 2010?United States in 2010?

Easy. Let's just do some Googling:1. 12,966, FBI, Crime in the United States 2010.2. 13,164, FBI, Crime in the United States 2011 (2010 figure).3. 14,720, Bureau of Justice Statistics (Table 1, based on FBI, Supplementary Homicide

Statistics).4. 16,259, CDC (based on death certificates in the National Vital Statistics System).

Between the smallest and largest figures there is a difference of 3,292 deaths or 25%!

The differences are striking but not entirely arbitrary or without explanation. I assume the second figure adds late additions to the 2010 data and so should be considered more authoritative.

The difference between 1&2 and 3 is puzzling and seems to be that the lower figure is from data from the SHR when extra victim information is collected and not every agency reports to the SHR while 3 is when any report exists from the larger UCR.

The FBI collects data on crimes. If a killing is ruled justified, i.e. not a crime, it doesn't go into the FBI homicide statistics. The CDC collects data from death certificates which list as homicide any death caused by “injuries inflicted by another person with intent to injure or kill, by any means.” Thus, the CDC data includes justifiable homicide. In 2010 according to the FBI there were 387 justifiable homicides by law enforcement and 278 by private citizen for a total of 665 justifiable homicides, so that accounts for some but not all of the difference.

The FBI and NVSS figures track each other closely over time but its important to be aware of the differences.

NIBRSNIBRS The National Incident Based Reporting System (NIBRS) is an The National Incident Based Reporting System (NIBRS) is an

expansion of the UCR which is meant to collect more data expansion of the UCR which is meant to collect more data and make up for some of the deficiencies in the original UCR and make up for some of the deficiencies in the original UCR program.program.

Group A Group A

NIBRS OffensesNIBRS Offenses

ArsonAssaultBriberyBurglaryCounterfeitingDestruction/VandalismDrug OffensesEmbezzlementExtortionFraudGambling OffensesHomicide

Kidnapping/AbductionLarceny/Theft

Motor Vehicle TheftMotor Vehicle Theft

PornographyPornography

ProstitutionProstitution

RobberyRobbery

Sex Offenses, Sex Offenses, ForcibleForcible

Sex Offenses, Sex Offenses, NonforcibleNonforcible

Stolen PropertyStolen Property

Weapon Law Weapon Law ViolationsViolations

The UCR reports include the aggregate The UCR reports include the aggregate number of incidents by offense per number of incidents by offense per month. Under NIBRS agencies provide month. Under NIBRS agencies provide a record for each crime reported. a record for each crime reported. Information in the record will include a Information in the record will include a detailed description of the offense, the detailed description of the offense, the offender, victim, and the arrest data offender, victim, and the arrest data for the crime incident. for the crime incident.

Some differences between UCR and Some differences between UCR and NIBRSNIBRS– Records rapes of male victims (UCR Records rapes of male victims (UCR

only records rapes against women)only records rapes against women)– Distinguishes between attempted and Distinguishes between attempted and

completedcompleted– Provides details for more expanded Provides details for more expanded

crimescrimes– LinksLinks report and arrest data allowing report and arrest data allowing

e.g. time to arrest analysise.g. time to arrest analysis

NIBRSNIBRS The first pilot demonstration of NIBRS The first pilot demonstration of NIBRS

was done in 1987, and the system was done in 1987, and the system was approved in 1988. was approved in 1988.

Not all states report to NIBRS. Not all states report to NIBRS. Only some agencies within a state Only some agencies within a state

report so one cannot run cross-report so one cannot run cross-sectional analyses, e.g. you can’t run sectional analyses, e.g. you can’t run cross-state regressions since the cross-state regressions since the number of agencies reporting in each number of agencies reporting in each state differs.state differs.

Until more agencies begin Until more agencies begin participating, the FBI continues to participating, the FBI continues to report statistics in the traditional report statistics in the traditional format by converted NIBRS data into format by converted NIBRS data into summary format.summary format.

NIBRS data since 1995 is available NIBRS data since 1995 is available from National Archive of Criminal from National Archive of Criminal Justice housed in the Inter-University Justice housed in the Inter-University Consortium for Political and Social Consortium for Political and Social Research at the University of Research at the University of Michigan. Michigan. The NIBRS Program Guide offers useful information.offers useful information.

NIBRS databases are larger and NIBRS databases are larger and difficult to work with.difficult to work with.

YearGroup A Offenses

Group B Offenses

Participating Agencies

1995 837,014 318,524 1,2551996 1,064,763 387,622 1,4871997 1,426,978 531,097 1,7381998 1,822,675 713,057 2,2491999 2,157,326 830,071 2,8522000 2,841,523 1,006,424 3,3652001 3,232,281 1,044,178 3,6112002 3,455,589 1,126,216 3,8092003 3,637,432 1,154,498 4,2872004 4,083,571 1,296,557 4,5252005 4,614,054 1,457,435 4,6822006 4,906,781 1,540,038 4,841

National Crime Victimization National Crime Victimization SurveysSurveys

Not all crimes are reported to police, and thus the Uniform Crime Not all crimes are reported to police, and thus the Uniform Crime Reports, even with the NIBRS expansion, underreport the actual Reports, even with the NIBRS expansion, underreport the actual amount of crime that is taking place.amount of crime that is taking place.

Victimization survey can tell us about unreported crime and also Victimization survey can tell us about unreported crime and also more about age, sex, race, income etc. of victims, more about age, sex, race, income etc. of victims, even marriage status and crime..

The National Crime Victimization Surveys (NCVS), administered by The National Crime Victimization Surveys (NCVS), administered by the U.S. Census Bureau, was started in 1972 and has been the U.S. Census Bureau, was started in 1972 and has been ongoing since then. The household is the main unit of analysis. ongoing since then. The household is the main unit of analysis. The sample size has being growing smaller due to budget cuts, The sample size has being growing smaller due to budget cuts, began around 72,000 now around 40,000. began around 72,000 now around 40,000.

NCVS is available through NACD the NCVS is available through NACD the NCVS Resource Guide offers offers useful information. useful information.

National Crime Victimization National Crime Victimization SurveysSurveys

The NCVS uses three instruments when conducting surveys The NCVS uses three instruments when conducting surveys of households:of households:– Control Card: Collects basic information about household Control Card: Collects basic information about household

including address and demographics of those that reside there. including address and demographics of those that reside there. Also includes a record of visits, interviews, and telephone Also includes a record of visits, interviews, and telephone contactcontact

– Screen questionnaire: asks information about possible Screen questionnaire: asks information about possible victimizations victimizations

– Incident report: further questions about victimization that took Incident report: further questions about victimization that took place including whether it was reported to the police, place including whether it was reported to the police, information about the offender and location of the crime, and information about the offender and location of the crime, and whether the crime was attempted or completed.whether the crime was attempted or completed.

The interviewers ask questions about attempted or The interviewers ask questions about attempted or completed: thefts, burglaries, auto thefts, assaults, rape or completed: thefts, burglaries, auto thefts, assaults, rape or other sexual attacks and more recently about vandalism other sexual attacks and more recently about vandalism and identity theft.and identity theft.

NCVS was redesigned in 1992 to change the wording of NCVS was redesigned in 1992 to change the wording of questions. This redesign led to increased recall of questions. This redesign led to increased recall of victimization incidents by respondents, which compromises victimization incidents by respondents, which compromises the comparability of survey results prior to 1992 to those the comparability of survey results prior to 1992 to those after 1992.after 1992.

Budget cuts have made the survey sample smaller over Budget cuts have made the survey sample smaller over time.time.

National Crime Victimization National Crime Victimization SurveysSurveys

ProsPros ConsCons More accurate measures of true More accurate measures of true rates of crime, especially for violent rates of crime, especially for violent crimes (minus homicide)crimes (minus homicide) More information about the crime is More information about the crime is collected (day, time, location, collected (day, time, location, relationship of victim and perpetrator, relationship of victim and perpetrator, etc…)etc…)

Results are aggregated at the Results are aggregated at the national level and not reported for national level and not reported for different jurisdictions different jurisdictions Some crimes such as prostitution are Some crimes such as prostitution are considered victim-less and thus are considered victim-less and thus are not included in victimization surveysnot included in victimization surveys Some crimes have no victims to Some crimes have no victims to interview (homicide)interview (homicide) Sampling error/bias issuesSampling error/bias issues Possibilities of different definitions of Possibilities of different definitions of crimes across different social groups crimes across different social groups (e.g. college educated report more (e.g. college educated report more assaults.)assaults.)

The results of the surveys are published annually in The results of the surveys are published annually in Criminal Criminal Victimization in the United StatesVictimization in the United States

Data on the number and rates from crimes reported via the NCVS Data on the number and rates from crimes reported via the NCVS from 1995-continuing can be obtained from National Archive of from 1995-continuing can be obtained from National Archive of Criminal Justice housed in the Inter-University Consortium for Criminal Justice housed in the Inter-University Consortium for Political and Social Research at the University of MichiganPolitical and Social Research at the University of Michigan

Comparing UCR and NCVSComparing UCR and NCVS According to data from the NCVS most crimes are not reported to According to data from the NCVS most crimes are not reported to

police. In 2006 38% of property crimes and about 50% of violent police. In 2006 38% of property crimes and about 50% of violent crimes were reported.crimes were reported.

In 2004 the UCR indicated that there were 2.91 aggravated In 2004 the UCR indicated that there were 2.91 aggravated assaults per 1,000, where as the NCVS indicated 4.3 per 1,000. assaults per 1,000, where as the NCVS indicated 4.3 per 1,000. Similarly the UCR indicated 4.21 motor vehicle thefts per 1,000 Similarly the UCR indicated 4.21 motor vehicle thefts per 1,000 while the NCVS indicated 8.4 motor vehicle thefts per 1,000.while the NCVS indicated 8.4 motor vehicle thefts per 1,000. The two measures often show The two measures often show

trends that move in the same trends that move in the same direction, but not always (Rand direction, but not always (Rand and Rennison 2002)and Rennison 2002)

The UCR includes homicide, but The UCR includes homicide, but the NCVS does not; the NCVS the NCVS does not; the NCVS includes simple assault which includes simple assault which the UCR does not.the UCR does not.

The top two lines are from NCVS, the bottom two from UCR

International Crime Data International Crime Data (ICVS)(ICVS)

The International Crime Victimization Survey (ICVS) became The International Crime Victimization Survey (ICVS) became operational in 1989, with subsequent installments in 1992, 1996, operational in 1989, with subsequent installments in 1992, 1996, 2000, and 2004-5. It is the most ambitious and comprehensive 2000, and 2004-5. It is the most ambitious and comprehensive attempt to minimize the myriad of difficulties associated with attempt to minimize the myriad of difficulties associated with making cross-country comparisons of crime victimization. Data making cross-country comparisons of crime victimization. Data are available in SPSS and SPSS Portable formats and can be are available in SPSS and SPSS Portable formats and can be downloaded from downloaded from http://www.unicri.it/wwd/analysis/icvs/data.phphttp://www.unicri.it/wwd/analysis/icvs/data.php. . Sample questionnaires are available at Sample questionnaires are available at http://rechten.uvt.nl/icvs/#Questionnaireshttp://rechten.uvt.nl/icvs/#Questionnaires. .

The 1989 sweep included 14 industrialized countries; several city-The 1989 sweep included 14 industrialized countries; several city-specific surveys were also administered in the first installment. . specific surveys were also administered in the first installment. . The most recent installment included responses from individuals The most recent installment included responses from individuals in 30 countries as well as 33 city-specific surveys. The ICVS uses a in 30 countries as well as 33 city-specific surveys. The ICVS uses a standard sample population size of 2000 individuals for each standard sample population size of 2000 individuals for each country.country.

Over the course of the survey, more than 300,000 individuals from Over the course of the survey, more than 300,000 individuals from 78 countries have participated in the ICVS. Five countries, Canada, 78 countries have participated in the ICVS. Five countries, Canada, England & Wales, Finland, Netherlands, and USA, have England & Wales, Finland, Netherlands, and USA, have participated in all five rounds of the ICVS. participated in all five rounds of the ICVS.

0 .5 1 1.5 2 2.5Robbery

JapanNorthern Ireland

USAFinland

DenmarkScotland

Catalonia (Spain)Switzerland

CanadaPortugalBelgiumAustralia

NetherlandsSwedenFrance

England & WalesPoland

0 1 2 3 4 5Burglary

FinlandFrance

SwitzerlandCatalonia (Spain)

ScotlandJapan

Northern IrelandPortugal

NetherlandsSwedenBelgiumPoland

CanadaDenmark

USAEngland & Wales

Australia

0 2 4 6 8Sexual Incidents

PolandCatalonia (Spain)

PortugalFrance

Northern IrelandBelgiumScotland

USAJapan

SwitzerlandCanada

DenmarkNetherlands

SwedenEngland & Wales

AustraliaFinland

0 5 10 15Assaults and Threats

JapanPortugal

Catalonia (Spain)Switzerland

Northern IrelandBelgium

DenmarkNetherlands

PolandFranceFinland

SwedenUSA

CanadaScotlandAustralia

England & Wales

Source: Van Kesteren, J.N., Mayhew, P. & Nieuwbeerta, P. (2000) 'Criminal Victimisation in Seventeen Industrialised Countries: Key-findings from the 2000 International Crime Victims Survey'.The Hague, Ministry of Justice, WODC.

Offenses Per 100 Inhabitants, 2000Crime in USA and other Industrialized Countries

Homcide Rates by CountryHomcide Rates by Country

The ICVS does not The ICVS does not compare homicide compare homicide across countries and across countries and the definition of the definition of homicide can vary. homicide can vary. Unfortunately, there Unfortunately, there is no central source is no central source of comparable of comparable homicide data but on homicide data but on any reasonable any reasonable comparison the comparison the United States does United States does have a high homicide have a high homicide rate relative to other rate relative to other industrializedindustrialized nations nations as shown in Figure 7. as shown in Figure 7. Thus, it is the U.S. Thus, it is the U.S. homicide rate not homicide rate not the U.S. crime rate the U.S. crime rate which stands as the which stands as the outlier.outlier.

0 2 4 6

DenmarkIreland

NetherlandsJapan

AustraliaEngland & Wales

BelgiumFrancePoland

PortugalCanadaSweden

ScotlandFinland

SwitzerlandSpainUSA

Circa 2000-2007, depending on country.Note: Definitions of homicide may vary by country.Source: Various by country as compilied by Wikipedia.

Rate per 100,000Homicide Rate by Country

Recidivism of Prisoners Released Recidivism of Prisoners Released in 1994in 1994

In 1997 the BJS collected data from 15 departments In 1997 the BJS collected data from 15 departments of corrections and compiled the of corrections and compiled the complete criminal complete criminal history history of a sample of prisoners released in 1994.of a sample of prisoners released in 1994.

The data on each released prisoner comes from the The data on each released prisoner comes from the officially recorded history captured in the FBI and officially recorded history captured in the FBI and State RAP Records of Arrests and Prosecutions) State RAP Records of Arrests and Prosecutions) sheets. sheets.

Thus constructed, the data contains information Thus constructed, the data contains information from the releasees first arrest to the end of the from the releasees first arrest to the end of the sample period in 1997.sample period in 1997.

The file is arranged by released prisoner and The file is arranged by released prisoner and contains up to 99 “arrest cycles.” Each cycle is contains up to 99 “arrest cycles.” Each cycle is determined by the date of arrest and includes determined by the date of arrest and includes details on the crimes committed (i.e. arrested for details on the crimes committed (i.e. arrested for assault and burglary if the arrest occurred at the assault and burglary if the arrest occurred at the same time) the adjudication (i.e.. plead guilty and same time) the adjudication (i.e.. plead guilty and given 6 months). The data on arrest and given 6 months). The data on arrest and adjudication are very detailed as each charge of the adjudication are very detailed as each charge of the arrest has multiple codings for the crime arrest has multiple codings for the crime committed, whether the charge was a felony or a committed, whether the charge was a felony or a misdemeanor as well as information about the misdemeanor as well as information about the victims. victims.

Very difficult data to work with.Very difficult data to work with.

Tracked Prisoners by State from Recidivism of Prisoners Released in

1994

StateReleased Prisoners

Arizona 2,000California 7,183Delaware 721

Florida 2,893Illinois 2,615

Maryland 2,117Michigan 2,315

Minnesota 1,929New

Jersey 2,289New York 2,639

North Carolina 2,314

Ohio 2,664Oregon 2,292

Texas 2,550Virginia 2,103

Total 38,624

Other data sourcesOther data sources From the Bureau of Justice statistics you can also find data about:From the Bureau of Justice statistics you can also find data about:

– Law Enforcement: Law Enforcement Management and Administrative Law Enforcement: Law Enforcement Management and Administrative Statistics Survey (LEMAS). Conducted in 2000Statistics Survey (LEMAS). Conducted in 2000

Covers primary state law enforcement agencies, and local police agencies Covers primary state law enforcement agencies, and local police agencies with 100 or more sworn officers and 50 or more uniformed officerswith 100 or more sworn officers and 50 or more uniformed officers

Includes budget, number of employees (broken down by demographics and Includes budget, number of employees (broken down by demographics and gender), types of patrols, salaries, special units, vehicles, and community gender), types of patrols, salaries, special units, vehicles, and community policing activities.policing activities.

Easy access here. NACJD Program Guide.Easy access here. NACJD Program Guide.– Corrections. Including:Corrections. Including:

Reports of number of prisoners in State and Federal prisons. Reports called Reports of number of prisoners in State and Federal prisons. Reports called Prisoners in xxxxPrisoners in xxxx and are available from 1994-2005 on the BJS website and are available from 1994-2005 on the BJS website

Drug Use and Dependence in State and Federal Prisons, 2004Drug Use and Dependence in State and Federal Prisons, 2004 Mental Health Problems: self-reported information on mental health of Mental Health Problems: self-reported information on mental health of

prisonersprisoners Sexual Violence Reported by Correctional Authorities, 2005Sexual Violence Reported by Correctional Authorities, 2005 Recidivism of Prisoners Released in 1994Recidivism of Prisoners Released in 1994

– Courts and Sentencing. Including:Courts and Sentencing. Including: National Judicial Reporting Program: biannual survey of felony trial courts. National Judicial Reporting Program: biannual survey of felony trial courts.

Includes information on demographic characteristics of felons, conviction Includes information on demographic characteristics of felons, conviction offenses, type of sentences, sentence lengths, and time from arrest to offenses, type of sentences, sentence lengths, and time from arrest to conviction. Data from 1983-2002 available on BJS websiteconviction. Data from 1983-2002 available on BJS website

State Court Processing Statistics: provides data on the criminal justice State Court Processing Statistics: provides data on the criminal justice processing of persons charged with felonies in 40 jurisdictions processing of persons charged with felonies in 40 jurisdictions representative of the 75 largest counties. 1988-2002 data available online. representative of the 75 largest counties. 1988-2002 data available online.

NLSYNLSY The National Longitudinal Survey of Youth (NLSY) is another survey The National Longitudinal Survey of Youth (NLSY) is another survey

useful for crime data. This survey is meant to document the useful for crime data. This survey is meant to document the transition from adolescence to adulthood. transition from adolescence to adulthood.

NLYS periodically surveys a representative sample of youths ages NLYS periodically surveys a representative sample of youths ages 12-17 about various aspects of their life such as income and jobs, 12-17 about various aspects of their life such as income and jobs, family history, expectations, attitudes and behavoirs, and use of family history, expectations, attitudes and behavoirs, and use of time (including in criminal activities). time (including in criminal activities).

Thus, unlike the NCVS, the NLSY uses self-reports of offending rather Thus, unlike the NCVS, the NLSY uses self-reports of offending rather than victimization. Respondents are asked about their drug use, than victimization. Respondents are asked about their drug use, handgun use, type of crimes committed, and amount of illegal drugs handgun use, type of crimes committed, and amount of illegal drugs sold or used.sold or used.

Data is reported at the individual level rather than at the household Data is reported at the individual level rather than at the household level.level.

Data from the NLYS 1979 and 1997 are available from the Bureau of Data from the NLYS 1979 and 1997 are available from the Bureau of Labor Statistics. Labor Statistics.

Again, this data is also available from National Archive of Criminal Again, this data is also available from National Archive of Criminal Justice housed in the Inter-University Consortium for Political and Justice housed in the Inter-University Consortium for Political and Social Research at the University of MichiganSocial Research at the University of Michigan

Geographic Crime DataGeographic Crime DataCrime Mapping and Spatial AnalysisCrime Mapping and Spatial Analysis

Crime mapping has a Crime mapping has a long history, going back long history, going back to the Cartographic to the Cartographic school Quetelet (1831) school Quetelet (1831) and Mayhew (1861), but and Mayhew (1861), but crime mapping did not crime mapping did not become an important become an important tool in crime fighting until tool in crime fighting until the 1990s when police the 1990s when police departments, led by the departments, led by the NYPD, made the weekly NYPD, made the weekly collection and analysis of collection and analysis of data the central data the central organizing principle of organizing principle of police strategy.police strategy.

Source: Encyclopedia of Crime and Punishment: Volumes I-IVBy David Levinson, SAGE, 2002. Originally in Mayhew, Henry. 1861-1862 [1968] London Labour and the London Poor, volume 4. New York: Dover, p. 467.

Geographic Crime DataGeographic Crime Data Many large police departments now have Many large police departments now have

statistical units that collate, manage, and statistical units that collate, manage, and analyze crime databases. With the rise of the analyze crime databases. With the rise of the internet it became a natural and simple internet it became a natural and simple procedure to export crime data to the web for procedure to export crime data to the web for use by the public. The LA, Chicago, use by the public. The LA, Chicago, Washington, Oakland, and Baltimore police Washington, Oakland, and Baltimore police departments, among others, offer online departments, among others, offer online mapping of crime incidents, usually from the mapping of crime incidents, usually from the past several months.past several months.

Websites such as SpotCrime collate data from Websites such as SpotCrime collate data from many police departments around the United many police departments around the United States and produce maps on request using States and produce maps on request using online tools such as Google Maps. online tools such as Google Maps.

GeocodingGeocoding Crime data from police departments will typically come in the Crime data from police departments will typically come in the

form of addresses (typically redacted to the block level). The first form of addresses (typically redacted to the block level). The first step in analysis is to geocode the addresses, that is assign step in analysis is to geocode the addresses, that is assign geographic identifiers to each address.geographic identifiers to each address.

For example, we obtained data on over 285,000 crimes from For example, we obtained data on over 285,000 crimes from January of 1997 to July of 2003 from the Metropolitan Police January of 1997 to July of 2003 from the Metropolitan Police Department of the District of Columbia. For each address, we paid Department of the District of Columbia. For each address, we paid Geocode.com to link the address to longitude and latitude Geocode.com to link the address to longitude and latitude coordinates, zip code, and most importantly Census tract and coordinates, zip code, and most importantly Census tract and block group codes.block group codes.

Census block groups are the smallest geographical unit for which Census block groups are the smallest geographical unit for which the bureau publishes sample data. The census aims for a the bureau publishes sample data. The census aims for a population of 1500 in each census block group. (In Washington, population of 1500 in each census block group. (In Washington, DC there are 433 Census block groups with a mean population of DC there are 433 Census block groups with a mean population of 1321.)1321.)

Using the Census block group codes one can merge geocoded Using the Census block group codes one can merge geocoded crime data with data from the Census. Census Data is available crime data with data from the Census. Census Data is available from the U.S. Bureau of the Census in many different forms. One from the U.S. Bureau of the Census in many different forms. One of the most convenient is the online download tool. of the most convenient is the online download tool.

MappingMapping The The U.S. Bureau of the CensusU.S. Bureau of the Census encodes geographic information in TIGER/Line encodes geographic information in TIGER/Line®®

files. Conveniently if the Census breaks data down by a type of region it will files. Conveniently if the Census breaks data down by a type of region it will typically also be possible to use Tiger/Line data to map the regions. Tiger files, typically also be possible to use Tiger/Line data to map the regions. Tiger files, for example, encode geographic information such as boundaries for Census for example, encode geographic information such as boundaries for Census Block Groups, Census Blocks, Census Tracts, Counties, Congressional Districts, Block Groups, Census Blocks, Census Tracts, Counties, Congressional Districts, School Districts and Voting Districts. Tiger/Line files can also include School Districts and Voting Districts. Tiger/Line files can also include information on railroads, roads, landmarks and other geographic features. information on railroads, roads, landmarks and other geographic features.

Data from Tiger Line files can be exported as “shape files.” Shape files are a Data from Tiger Line files can be exported as “shape files.” Shape files are a set of formats for geographic data developed by ESRI, a leading producer of set of formats for geographic data developed by ESRI, a leading producer of software for spatial analysis. Tiger Line shape files can be access from the software for spatial analysis. Tiger Line shape files can be access from the U.S. U.S. Bureau of the CensusBureau of the Census or more conveniently through ESRI where you can or more conveniently through ESRI where you can download Census 2000 Tiger Line data by state and according to a wide variety download Census 2000 Tiger Line data by state and according to a wide variety of layers such as Census Block Groups, Census Blocks, Census Tracts, and so of layers such as Census Block Groups, Census Blocks, Census Tracts, and so forth. We obtain boundary data on Census Block Groups for Washington, DC in forth. We obtain boundary data on Census Block Groups for Washington, DC in the form of shape files from ESRI.the form of shape files from ESRI.

STATA has no built in functions for producing maps or using shape files. But STATA has no built in functions for producing maps or using shape files. But two packages provide considerable functionality. SHP2DTA converts shape files two packages provide considerable functionality. SHP2DTA converts shape files to STATA dta files in a format that SPMAP can to produce maps. Both packages to STATA dta files in a format that SPMAP can to produce maps. Both packages can be easily installed in STATA using the ssc install command. The key to can be easily installed in STATA using the ssc install command. The key to using these packages is to ensure that the location identifier in the map data is using these packages is to ensure that the location identifier in the map data is the same as the location identifier in the Census data that you wish to map.the same as the location identifier in the Census data that you wish to map.

Useful information can be found regarding STATA maps here.Useful information can be found regarding STATA maps here.

MappingMapping The DC metropolitan police department collects data on all crimes The DC metropolitan police department collects data on all crimes

reported to police. This data includes offense type (Homicide, reported to police. This data includes offense type (Homicide, Robbery, Theft from auto, etc..), date of offense, hour of offense Robbery, Theft from auto, etc..), date of offense, hour of offense (0-24), and location.(0-24), and location.

Data currently includes all offenses reported to the DC police from Data currently includes all offenses reported to the DC police from 1/1/1997 to 7/30/2003. It may be possible to update this to the 1/1/1997 to 7/30/2003. It may be possible to update this to the present date by contacting the Metropolitan Police Department.present date by contacting the Metropolitan Police Department.

This data was used in Jon Klick and Alex Tabarrok. 2005. Using This data was used in Jon Klick and Alex Tabarrok. 2005. Using Terror Alert Levels to Estimate the Effect of Police on Crime.Terror Alert Levels to Estimate the Effect of Police on Crime. Journal of Law and EconomicsJournal of Law and Economics:48(1):48(1)

Similar problems can exist with this data as did with the UCR data, Similar problems can exist with this data as did with the UCR data, and as noted before not all crimes are reported to police and this and as noted before not all crimes are reported to police and this dataset only includes those reported.dataset only includes those reported.

MappingMapping The data can be used to analyze the impact of policies or events The data can be used to analyze the impact of policies or events

on locations, rates, or times of crime, as in Klick and Tabarrok on locations, rates, or times of crime, as in Klick and Tabarrok (2005).(2005).

It can also be used for spatial analysis using graphing, spatial It can also be used for spatial analysis using graphing, spatial econometrics, or hot spot analysis.econometrics, or hot spot analysis.

An example of figures that can be obtained from the data:An example of figures that can be obtained from the data:

[0.00,0.00](0.00,1.12](1.12,3.11](3.11,5.95](5.95,1500.00]

These figures These figures compare compare locations of locations of homicides to homicides to homicide rates homicide rates per 1,000 in the per 1,000 in the populationpopulation

Spatial EconometricsSpatial Econometrics It is clear from the maps that crime and its It is clear from the maps that crime and its

demographic correlates are not distributed demographic correlates are not distributed randomly over space. Thus, regressions which do randomly over space. Thus, regressions which do not take into account spatial clustering or spatial not take into account spatial clustering or spatial autocorrelation can be misleading.autocorrelation can be misleading.

Spatial clustering of errors is used fairly often in Spatial clustering of errors is used fairly often in economics although in geographic data the economics although in geographic data the clusters are not always obvious, Census block? clusters are not always obvious, Census block? City? Region?City? Region?

Spatial correlation, analogous to temporal Spatial correlation, analogous to temporal correlation, recognizes that events in space may correlation, recognizes that events in space may not be independent. An increase in crime in one not be independent. An increase in crime in one region, for example, may predict an increase in region, for example, may predict an increase in crime in neighboring regimes through a variety of crime in neighboring regimes through a variety of spillover processes. Temporal correlation is spillover processes. Temporal correlation is relatively easy to model but spatial correlation is relatively easy to model but spatial correlation is much more difficult. much more difficult.

Spatial EconometricsSpatial Econometrics Key difficulty is that Key difficulty is that

defining the defining the “neighborhood” over “neighborhood” over which correlation occurs which correlation occurs is not obvious.is not obvious.

Distance measure?Distance measure? Contiguity measure?Contiguity measure? Gravity Model?Gravity Model? Time-Space measures?Time-Space measures? Spatial econometrics Spatial econometrics

requires special requires special techniques and is a techniques and is a rapidly growing field of rapidly growing field of research.research.

D.C. Homicides

Petty would be PleasedPetty would be Pleased Today we can measure vice and Today we can measure vice and

sin across time and space, we sin across time and space, we can map it, correlate it, and can map it, correlate it, and crunch it as never before.crunch it as never before.

The amount of crime data is The amount of crime data is growing.growing.

Local crime data, including Local crime data, including geographic information, for geographic information, for example, is exploding at a rapid example, is exploding at a rapid pace and will be a key area for pace and will be a key area for criminology and econometric criminology and econometric research.research.

We hope that this paper will We hope that this paper will help to guide researchers to the help to guide researchers to the data that is most useful to data that is most useful to answering their questions. answering their questions.

Sir William Petty(1623-1687)

Source: Bowood House