Outdoor Lighting and Crime - Amper

Unlike the situation in England and Wales, however, usable crime data for the USA spanning
the twentieth century were not found. Most of the available time-series data for US crime
only covers recent decades. Inspection of Bureau of Justice Statistics data starting in 1973
(BJS 2002a) indicated that correlations of surveyed property and violence crime rates with
skyglow and population would be small or negative. However, correlations with recorded
violent crime and arrest rates still appear to be positive.
Annual crime rate data for the USA from 1960 are given by Maguire and Pastore (2002, Table
3.120), based on BJS Uniform Crime Reports (UCR) data. For years 1933 to 1959, the source
was JRSA (2000). The total of property and violent crime rate, including homicide, is called
the Total Crime Index or the Index Crime Rate, shown in Figure 3. The discontinuity at 1959
is an artifact resulting from change to the dollar limit for larceny. The 2001 results
(Butterfield 2002) are not shown in the figure: the UCR rate increased by 2.1 % over the 2000
value, ending the ten-year decline. During 2001, robberies climbed 3.7 percent, burglaries 2.9
percent, petty thefts 1.5 percent and motor vehicle thefts 5.7 percent.
No regional or national skyglow data were readily available so the skyglow curve used in
Figure 1 is used again as representative of exponential growth of skyglow near cities. US
population (Demographia 2002), the combined adult and juvenile estimated drug arrests rate
(BJS 2002a) and the total US federal and state rate (BJS 2002a) are also included in Figure 3.
The incarceration rate was included as it could possibly account for at least part of the
reduced growth or falling trend of crime in the US while the various factors conducive to
crime presumably continue to increase. 20, 21 Over half of the steep increase in US prison
population since 1990 is a result of convictions for violence.
Drug offences were included in Figure 3 as an exception to the flatter trends for most other
crime in the US over recent decades. All or most of the difference in growth rates may well
be caused by factors other than any effects of lighting. At first sight there might seem to be
no good reason to expect any direct connection at all between lighting and drugs crime.
However, exposure to artificial light at night already appears to have reached levels great
enough in some cases to reduce the production of melatonin by the pineal gland (see Section
6.1.4 below). This is so both in the evening and then later in the small hours when this part of
the human endocrine system appears to be most sensitive to small amounts of light. 22 If drug
20 A June 2002 public release of statistics showed that the prison population in Australia
increased by 50% in the decade from 1990. As a population rate, the increase is about 85% of
that in the USA.
21 Walker (2002) cautioned against drawing too much from incarceration rates as they might
be supposed to affect crime rates. Regardless, Weatherburn (2002) cited Spelman (year?) as
the best conducted review on the topic, with a conclusion that a 10% rise in the US prison
population reduces serious crime by between 2 and 4%.
22 The light receptors involved in the inhibition of melatonin production have their peak
sensitivity in the blue part of the spectrum. Low-pressure sodium lamps emit virtually no
blue light and therefore allow seeing with little effect on these receptors. Under-run highpressure
sodium lamps and normally operated high-pressure sodium lamps are progressively
less useful in this regard. Metal halide and mercury lamps are even richer in blue light and
therefore worse again. All else being equal, however, visibility in dim conditions is better
with bluish light, thereby creating a dilemma.
14