Outdoor Lighting and Crime - Amper

On the basis that there do not appear to have been large changes overall in the shading of
installed outdoor light fittings against upward light spill in recent decades and that probably
only small changes have occurred in the amount of light reflected upward from the terrain, the
plotted skyglow curve in Figure 1 is considered to indicate how the total of artificial ambient
light outdoors at ground level has grown in recent decades over the more densely populated
areas of Australia. The growth rate has probably been greatest in the state capital cities, and
slowest in rural areas. Determining the actual lighting growth rate in rural areas using
skyglow observations is complicated by the additive effects of waste light from distant cities
and nearby towns. Examples of this are given by Berry (1976), Cinzano (2000c,d) and
Dudley (2000). Note that luminance, rather than log luminance, is additive.
The form of the skyglow curve in Figure 1 can reasonably be supposed to be typical for most
of the highly urbanised Australian population. Of course, long runs of frequent observations
of skyglow in various locations would be better to work with, but so far, few Australian
skyglow observations seem to have been published.
Figure 1 also shows three sets of Australian recorded crime data. These data were selected on
the basis of being available, appropriate and freely accessible through the Internet for ease of
checking and comparing by others. 15 Data for homicide were also available but not included
as the rate has not varied greatly over the whole century 16 (Graycar 2001). The numbers for
homicide are so small relative to those for other crimes that they would make no practical
difference anyway in any overall number or rate. For the crime data that are shown in Figure
1, partition into day and night occurrence would be valuable but such data did not appear to
be available, either on the Internet or elsewhere.
The yearly crime rate data for 1974 to 1992 are from Walker (2002), for 1993 to 1999 from
Graycar (2001), and for 2000 and 2001 from ABS (2003). The usual basis of reporting crime
rate per 100 000 of the population has been changed proportionally to smaller population
numbers for convenience in plotting the data with a common ordinate scale. 17 The data are
not quite internally consistent and seamless because of evolving differences between state and
territory jurisdictions in definitions of crime, late numerical corrections and other relatively
minor perturbations. For example, data included as Burglary are called Unlawful Entry with
15 As an example of comparison, the growth rate of notifiable offences in England and Wales
between 1977 and 1999 was 85%, and in Northern Ireland, 50% (ONS 2000). Both of these
increases are less than the lowest growth rate for the three types of crime in Australia shown
in Figure 1, but are still substantial.
16 In Australia, nearly two-thirds of all homicides occurred in residences, and over two-thirds
of all homicides occurred between 6 pm and 6 am. Data over the century in other countries
also show that long-term changes in the homicide rate are much smaller than for other types
of crime. Regardless, Loomis, Marshall, Wolf, Runyan and Butts (2002) found that using
bright exterior lighting appeared to be one of several reliably beneficial measures against
workplace homicide at night in the USA, where homicide is the second leading cause of death
of employees at work.
17 The growth of crime has been so marked in some cases that rates per 100 of the population
are now sometimes convenient to use. Elsewhere in this document such rates are given as a
percentage, although this does not appear to be common practice among criminologists.
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