Outdoor Lighting and Crime - Amper

The homogeneity of the crime data is suspect. Much effort went into trying to assemble a
data set with crime rates for areas that approximated the areas given for the DMSP data. This
was possible to some extent with the London data which was available for individual
boroughs, but less so or not at all for the other cities. Maps of the police districts used
indicated that they sometimes extended from city centres or suburbs into semi-rural or rural
areas. In the London case, it was found possible to get several values of the crime rate
between 9% and 14.25% by choice of area covered, from the city centre and inner boroughs
to the whole of greater London. These crime rates did not vary monotonically with the
corresponding population. To avoid bias to the extent possible, the figures finally chosen for
all cities were simply as given in the references. The year chosen, 2000, was apparently the
earliest for which a ‘league table’ of crime in English cities had been published. 64 This is in
marked contrast to the situation in the USA, where the FBI’s Uniform Crime Reports data for
cities and counties have been publicly available for many years.
As a check on sensitivity to the contribution from London, the top-right data point was
removed temporarily. The slope reduced by 25% but the correlation coefficient increased
slightly, from 0.763 to 0.766. The slope retained its statistical significance: t = 3.154, 7 df, p
< 0.05. The result for English cities therefore appears to be robust, which is not to deny the
desirability of better quality data for crime, and for years closer to 1997. Light loss measures
for more cities and for other years would also be valuable. The present findings would appear
to justify the publication of crime figures for areas matching those used in the satellite
observations of light energy loss.
A regression analysis was also done for crime plotted against light energy loss per person
(figure not shown). The slope was –0.04, not significantly different from zero (t = 0.331, 8
df). Removing the London data point changed the slope to +0.03, again not statistically
significant. The Scottish cities showed a distinct upward trend on this plot but three data
points are still inadequate for a regression analysis.
64 It led to complaints of unfairness from cities with relatively small central populations. The
crime rates were claimed to be exaggerated by crimes committed by some of the nightly
influx of visitors.
75