Limitations
Studies that use NIBRS data have inherent limitations. First, when the NIBRS data show increases in crime over a period of years, it should not be assumed that the volume of criminal incidents in the Nation actually
increased. As seen in Table 1, such apparent increases from year to year may well be the result of increases
in the number of law enforcement agencies (1,934 more agencies over the 5-year period) reporting their UCR
data via the NIBRS format. As the percentage of agencies participating in the UCR Program via the NIBRS
increases and the NIBRS data become more representative of crime nationwide, data analysts will be better
equipped to identify increases and decreases in crime that are due to actual changes in crime volume rather
than to reporting. Furthermore, changes in proportions between groups should not be interpreted as an actual
change in the Nation’s crime characteristics. It is possible that demographics of the new reporting agencies are influencing the proportion (e.g., should the data show a sharp increase in the percentage of one particular
race of offender between two years). As more law enforcement agencies report via the NIBRS, analysts will be
more confident that the demographic characteristics of the data can be considered nationally representative. It is expected that, eventually, the NIBRS data, combined with other exogenous datasets, will allow researchers
to evaluate the effect of crime reduction policies in reducing crime. Another potential limitation is that the
agencies that submit their UCR data via the NIBRS format are not, for the most part, in large metropolitan
areas. In spite of these limitations, there have been studies that suggest that the NIBRS data may be representative of the Nation’s crime (see, for example, Section V of Crime in the United States, 2002, “Bank
Robbery in the United States”).
Another limitation of studies that use NIBRS data stems from the restricting level of disaggregation
possible when using NIBRS location codes. For example, crimes committed at school, college, and university
locations are all combined into a single NIBRS location code. Separating elementary and secondary schools from colleges is difficult, if not impossible, in the NIBRS format. The parameters available in NIBRS that
might help distinguish whether an incident took place at an elementary school, secondary school, or college are not mutually exclusive to any group. For example, there are many 17 year olds in college and, conversely, many
18 year olds in high school during the same period of time; therefore, age of victim, offender, or arrestee are not
variables that can identify whether the incident occurred in an elementary school, secondary school, or college.
In addition, neither the victim nor the offender necessarily attends the institution where the offense occurred.
Lastly, the validity of NIBRS data has not been tested; therefore, one should be cautious in the
interpretation of surprising findings, e.g., twelve 0-4 year old arrestees. (See Table 11.) However, since one
purpose of this study is to show the arrestee and offender information that can be gleaned from incidents
involving crime in school locations reported via the NIBRS, data such as these are included in the study.
Because of these limitations, the findings discussed in the present study cannot be generalized to the Nation
as a whole. Readers are advised to be cautious in applying the results of this study to other research.
School Violence Index
