Encyclopedia of Sociology

CRIME RATES

weeks,’’ and ‘‘once a month,’’ as well as asking the
exact number of times respondents offended dur-
ing the past year.

COMPARISONS OF CRIME RATES

GENERATED FROM UCR, NCVS, AND SELF-

REPORTS

Fortunately, the problems outlined above do not
mean that crime rates based on UCR, NCVS, and
self-reports are not useful. Homicide rates, for
example, are probably reasonably accurate in terms
of absolute rates and in terms of homicide trends
over the past sixty-five years. They also are appro-
priate for comparisons of homicide rates across
large cities. When we judge the usefulness and
accuracy of crime rates, the type of crime consid-
ered is important (e.g., homicide or rape). Fur-
ther, even if a crime rate is inaccurate in terms of
the absolute amount of crime it represents, it may
be an accurate measure of the relative amount of
that crime in different areas or across time. This
would be the case if exactly half or some other
proportion of the aggravated assaults were report-
ed in different jurisdictions (or across time). Then
we could perfectly compare the relative amount of
crime across jurisdictions (or crime trends over
time). If only approximately the same proportion
of cases were reported across jurisdictions, then
comparisons of the relative amount of crime would
only be approximate.

Measuring Absolute Crime Rates. The most
accurately measured UCR Part I crime almost
certainly is homicide. The reasons for this include
the seriousness of the crime and the physical
evidence it produces (e.g., a body, weapon, or
missing person), which make it unlikely that once
detected this crime will be ignored. Cantor and
Cohen (1980) compared homicide rates based on
the U.S. Department of Health, Education, and
Welfare’s Annual Vital Health Statistics Report with
those from the UCR for the years 1935–1975 and
found a very close correspondence. Using a differ-
ent approach, O’Brien (1996) found evidence that
fluctuations in the homicide rate closely paralleled
fluctuations in the rate of other violent crimes
from 1973 to 1992.

Motor vehicle theft is the other Part I crime
that appears to be well estimated in terms of

absolute rates. In 1994, for example, the NCVS

estimated 1,764,000 motor vehicle thefts based on

respondents’ answers, while the UCR reported

1,539,100 motor vehicle thefts known to the po-

lice. Thus the NCVS estimate exceeded the UCR

estimate by only 28 percent. When NCVS respon-

dents report a motor vehicle theft they are asked if

they reported the theft to the police. Based on

their responses one would calculate that the police

receive reports of only 1,379,448 motor vehicle

thefts, which is fewer motor vehicle thefts than

appear in the UCR records. This probably occurs

because motor vehicle thefts from private citizens

constitute only 80 to 85 percent of the total num-

ber of such thefts known to the police (Biderman

and Lynch 1991). For the remaining Part I crimes

covered by both the UCR and NCVS (personal

robbery, aggravated assault, residential burglary,

and rape), the NCVS and UCR data show greater

differences in absolute rates. The smallest ratio of

NCVS incidents to UCR incidents is 1.62 for rape

and the largest 3.01 for residential burglary.

Difficulties arise when comparing the self-

report rates to UCR and NCVS rates, because self-

report studies typically only involve a sample of

young people. The estimated crime rates for these

young people, however, are so high that we may

conclude that the rates generated by self-reports

are far greater than those generated by either the

NCVS or the UCR. The 1976 NYS produced an

estimated incident rate for eleven to seventeen

year-olds for aggravated assault of 170 per 1000

and for robbery a rate of 290 per 1000. This

compares with rates for those twelve year-olds and

over of 7.90 and 6.48 based on the NCVS and rates

for all ages of 2.29 and 1.96 based on the UCR.

Some part of this discrepancy results from differ-

ences in the age groups compared, but not all of it.

In 1976 eleven to seventeen year-olds comprised

13.38 percent of the population. Thus, even if it

were assumed that no assaults or robberies were

committed by other age groups, the aggravated

assault rate based on the NYS would be [.1338 ×

170 =] 22.75 and the rate for robbery would be

[.1338 × 290 =] 38.80.

Measuring Relative Crime Rates. If absolute

rates are well measured, then relative rates of

crimes across cities or other units probably are

well measured. This means that both homicide

rates and motor vehicle theft rates should be good