Encyclopedia of Sociology

CRIME RATES

crime raise difficult issues. To imagine the difficul-
ties consider two men at a bar. One of them makes
a rude comment to the other and the other person
shoves him. The person shoved strikes the other
person on the jaw before the fight is broken up.
The person hit on the jaw calls the police to the
scene and wants to press charges, but the person
shoved claims self-defense and that the person
who shoved him is guilty of an assault. The two
men may decide that the matter is not worth
pressing and the police may agree. On the other
hand, the police may file a report that results in an
arrest. If a grand jury thinks the evidence warrants
it, the case may go to trial. Even if the case reaches
trial, the jury may acquit the accused.Other possi-
ble steps in the process exist, but determining
whether a crime occurred is often difficult. The
process contains many decision points. Will the
individuals involved report the incident to the
police? Will the police determine that a crime
occurred? Now imagine that an interviewer asks
one of these men about their history of criminal
offending or victimization. Would the individual
report this incident to the interviewer? Would one
of the individuals admit to an interviewer that he
committed an assault? Crime counts constitute an
important element in the calculation of crime
rates, but they are only one factor.

Rather than report simple crime counts, social
scientists often calculate crime rates. Depending
on the context, they may do this because crime
rates: (1) allow for the comparison of crime pat-
terns across groupings of different sizes, (2) make
possible the comparison of the relative frequency
of crime over time, or (3) help in the assessment of
the risk of victimization. In terms of comparability
of patterns across groupings of different sizes,
simply reporting the number of crimes in cities
with 100,000 or more residents produces unsatis-
factory results. Forty homicides may not represent
a large number for New York City, but twenty
homicides represent a large number in Eugene,
Oregon. The calculation of homicide rates per
100,000 residents for New York City and Eugene
makes comparisons between the two cities easier.
Similar calculations of rates for different years
facilitate comparisons over time. The number of
homicides may have doubled in Los Angeles from
1920 to 1990 while the rate per 100,000 residents
has decreased. In terms of the risk of motor vehi-
cle theft, a rate based on the number of motor

vehicle thefts per 10,000 registered motor vehicles

may be more helpful than the number of motor

vehicles stolen.

Equation (1) represents the general formula

for calculating a crime rate:

( 1 )

Crime Rate Per Base =

x Base

Number of Incidents

()Relevant Population Size

Each of the components in this formula: Base,

Relevant Population Size, and Number of Inci-

dents, represents an important decision point when

calculating a crime rate. Determining the most

appropriate measure for each component is not as

straightforward as it might first appear.

Selecting a Base: If the base is 100,000, then the

interpretation of the rate is the number of inci-

dents per 100,000. With a base of 100 the interpre-

tation is in terms of the number of incidents per

100 (a percent). Reports of crime rates often ap-

pear as rates per 100,000 or per 10,000. One

reason for this is the relative infrequency of some

crimes. For example, in 1997 the number of mur-

ders in the United States was 18,210 and the

population of the United States was 268 million. If

we choose 100 for the base, we find that the

homicide rate per 100 is .0068 or .0068 percent.

This figure challenges the intuition of most peo-

ple. We should choose the base to make the rate

easier to interpret. If we choose 100,000 for the

base, we find that the homicide rate is 6.8 per

100,000; a much easier figure for most people to

understand.

Relevant Population Size: The choice of the

relevant population size depends upon the selec-

tion of an appropriate ‘‘relevant population.’’ The

Uniform Crime Reports (UCR) typically chooses

the number of residents as the relevant popula-

tion. This number is used to calculate crime rates

for cities or for the United States as a whole in the

UCR. The National Crime and Victimization Sur-

vey (NCVS) often uses the number of residents

who are twelve years of age or older as the relevant

population, since the survey only asks about crime

incidents involving those in that age range. At

other times households represent the relevant

population as when victimization surveys calculate

rates for households touched by crime.