Outdoor Lighting and Crime - Amper

affordability of domestic outdoor lighting for employees and in the number of employees who
might consider installing such lighting. Thus there is a bi-directionally causal relationship
between commerce and lighting. A similar relationship seems likely for commerce and
crime: increased commerce would appear to motivate criminals and increase the opportunities
for crime, while crime would appear to inhibit commerce. Lighting, commerce and crime
therefore appear to be related causally in most or all of the six possible directions between
pairs. On the evidence presented in this document, there is observational support for the
notion that lighting is a cause of crime, regardless of whether this comes about largely
through intermediate interactions with commerce or some other mechanisms.
As a means of increasing commerce, outdoor lighting also seems to be an important
contributory factor in the processes of urbanisation, urban intensification, urban utilisation
and urban sprawl, thereby possibly further accentuating growth in the crime rate. This is not
in conflict with the existing view that urbanisation “in any country generally begins when
large-scale commerce takes root and most new jobs are to be found in the factories and
financial centers in cities” (NASA 2000).
The six possible interactions are indicated in Table 2, along with effects and reasons that
appear to be important. The sign of an effect within an interaction is given as positive when
an increase in the causative variable produces an increase in the dependent variable.
Conversely, a negative sign indicates that the affected variable would decrease. Apparently
strong effects are indicated notionally in Table 2 by two or more signs. Two signs do not
necessarily imply twice the effect of one sign, but just a heuristic estimate that the effect is
generally stronger. In due course it may be possible to quantify the strength of interactions in
particular examples, eg as partial correlation coefficients and their positive and negative
constituents.
The entry marked * in the ‘Reasons’ column of Table 2 is the converse of imposed darkness
inhibiting crime, which is clearly causal from observations. It is strong evidence against the
notion that crime and lighting are unconnected quantities merely growing concurrently
because of separate reliance on economic conditions.
Here is a concise statement of the new hypothesis:
Outdoor artificial light, commerce and crime are causally interactive in all six
possible directions. The sign of effects in each interaction can be positive or
negative, or a mixture of both. Light leads commerce and commerce leads crime as
dominant overall effects. Light may lead or lag crime. The net overall effect is for
light to lead crime.
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