The Rules of Contagion

first night of the riots, it would end up being one of the worst affected
areas. In the months following the riots, Davies and his colleagues at
University College London decided to pick apart how such disorder
could develop.[52] Rather than trying to explain how or why a riot
starts, the team instead focused on what happens once it gets
underway. In their analysis, they divided rioting into three basic
decisions. The first was whether a person would participate in the riot
or not. The researchers assumed this depended on what was
happening nearby – much like a disease epidemic – as well as local
socioeconomic factors. Once someone decided to participate, the
second decision involved where to riot. Because a lot of the rioting
and looting was concentrated in retail areas, the researchers adapted
an existing model for how shoppers flow into such locations (several
media outlets described the London riots as ‘violent shopping’[53]).
Finally, their model included the possibility of arrest once a person
arrived at the rioting site. This depended on the relative number of
rioters and police, a metric Davies referred to as ‘outnumberedness’.
The model could reproduce some of the broad patterns seen
during the 2011 riots – such as the focus on Brixton – but it also
showed the complexity of these types of events. Davies points out
that the model was only a first step; there’s a lot more that needs to
be done in this area of research. One big challenge is the availability
of data. In their analysis, the UCL team only had information on the
number of arrests for riot-related offences. ‘As you can imagine, it’s a
very small and very biased subsample,’ Davies said. ‘It doesn’t
capture who could potentially engage in rioting.’ In 2011, the rioters
were also more diverse than might be expected, with groups
transcending long-standing local rivalries. Still, one of the benefits of
a model is that it can explore unusual situations and potential
responses. For frequent crimes like burglary, police can introduce
control measures, see what happens, then refine their strategy.
However, this approach isn’t possible for rare events, which might
only spark now and again. ‘Police don’t have riots to practise on
every day,’ Davies said.
For a riot to start, there need to be at least some people willing to
join. ‘You cannot riot on your own,’ as crime researcher John Pitts put