
J. E. RIGGS ET AL.
0.0
1.0
2.0
3.0
0.05.010.0 15.0 20.0 25.0 30.0 35.0 40.0
Accident Mortality Rate
Homicide Rate
Figure 8.
Homicide versus accident mortality rate (per 100,000) in US girls, aged
1 - 4 years, from 1940 thr ough 2005.
Discussion
Young child homicide is frequently related to child abuse
(Jenny & Isaac, 2006) or psychiatric dysfunction in a custodial
adult (Friedman et al., 2005; Nielssen et al., 2009). Head inju-
ries, drowning, and suffocation are the most frequent causes of
death due to homicide in young children (Reece & Sege, 2000;
Tung et al., 2006; Vanamo et al., 2001). Investigators have sug-
gested that the actual magnitude of fatal child abuse has been
underestimated (Crume et al., 2002; Herman-Giddens et al.,
1999). Beginning in the 1960’s to the 1980’s, the problem of
young child abuse and homicide became the focus of increased
societal attention (Adelson, 1961; Christoffel, 1984; Kempe et
al., 1962; Jason, 1983).
Similar to infants (Riggs & Hobbs, 2011), young child acci-
dent mortality rates in both boys and girls decreased over 85
percent in the United States between 1940 and 2005 (Tables 1
and 2, and Figures 3 and 4), reflecting improved societal injury
prevention and trauma management. Also similar to infants
(Riggs & Hobbs, 2011), young child homicide and accident
mortality rates were slightly higher in boys than in girls (Ta-
bles 1 and 2).
When classifying two mutually exclusive events, their rela-
tive natural frequency may be important. For example, if event
A and event B are potentially difficult to distinguish and event
A is much more frequent, there may be a tendency to bias clas-
sification towards event A. However, if event A becomes less
frequent and the sensitivity to recognizing event B is increasing,
there may be a tendency to bias classification towards event B.
This line of reasoning was suggested as contributing to the
observed increase in infant homicide rates in the United States
after 1980 (Riggs & Hobbs, 2011). In the case of young child
homicide, homicide rates in the US increased predominantly
during the period of time when the sum of young child homi-
cide and accident mortality remained relatively constant (Fig-
ures 1, 2, 5-8). This same phenomenon was also observed in
US infants. Infant homicide rates in the US increased during the
period of time when the sum of infant homicide and accident
mortality rates were relatively constant (Riggs & Hobbs, 2011).
Moreover, if the ratio of accident mortality to homicide mortal-
ity in young children is consistently declining (as shown in
Tables 1 and 2, and illustrated in Figures 3 and 4), during the
periods when the sum of accident mortality and homicide rates
are relatively constant and necessarily n eg a ti ve ly c or re l at ed , th e n
homicide rates that must go up. If accident mortality rates
where to go up during those periods, then the ratio of accident
mortality rates to homicide rates would have also had to in-
crease; and that did not occur.
These findings suggest that the logic rules governing two
mutually exclusive, collectively exhaustive, and relatively con-
stant sum events are consistent with and describe the observed
increased reported young child homicide rates in US boys and
girls. These logic rules may also explain why the influence of
declining young child accident mortality and increased societal
sensitivity to child abuse were not associated with continued
increasing young child homicide rates despite the fact that both
of these influences continued to occur after the critical time
periods when the sum of the rates of young child homicide and
accident mortality rates were relatively constant. Moreover, it
seems rather unlikely that societal violence in the United States
would have been increased against young children before 1980
(as observed in this study) and would have separately and dis-
tinctly increased against infants after 1980 (Riggs & Hobbs,
2011).
Epidemiological data is crucial in identifying and monitoring
societal problems. Classification mechanisms are routinely used
in the production of epidemiological data, and those classifica-
tion mechanisms can have significant societal implications and
consequences. This study suggests that the logic rules govern-
ing mutually exclusive, collectively exhaustive, and constant
sum events described the classification process of distinguish-
ing young child accidental deaths from homicides, similar to
what was observed in US i nfants (Riggs & Hobbs, 2011 ). More-
over, these findings suggest that the increase in the homicide
rates observed among young US children may have reflected
the necessary negative correlation between mutually exclusive,
collectively exhaustive, and constant sum events rather than an
actual increase in societal violence directed against young chil-
dren, similar to the pattern observed after 1980 among US in-
fants. These observations illustrate the potential hazard of fo-
cusing attention on the measurement of one mutually exclusive
event (the homicide rate) without also considering the influence
of the other mutually exclusive event (the accident mortality
rate). This changing classification propensity, as demonstrated
in this study, appears to emerge spontaneously in the epidemi-
ological classification process of events that are mutually ex-
clusive, collectively exhaustive, and that have a relative con-
stant sum. Moreover, this changing classification propensity ap-
pears to occur despite the best intentions and expertise of all
those individuals who are independently involved in the classi-
fication process of each such unnatural death in young children.
Child abuse and homicide is a serious societal problem that
cannot be tolerated. However, the inaccurate classification of a
young child death as a homicide, rather than an accident, also
has unacceptable and intolerable consequences.
This study only examined unnatural mortality classified and
reported as either homicide or non-motor vehicle accident mor-
tality. This study did not examine natural mortality due to ill-
ness. Consequently, no inferences can, or should, be derived
from this study regarding misclassification between natural and
unnatural deaths.
REFERENCES
Adelson, L. (1961). Slaughter of the innocents, a study of forty-six
homicides in which the victims were children. New England Journal
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