  We build an agent-based model of incarceration based on the SIS model of
infectious disease propagation. Our central hypothesis is that the observed
racial disparities in incarceration rates between Black and White Americans can
be explained as the result of differential sentencing between the two
demographic groups. We demonstrate that if incarceration can be spread through
a social influence network, then even relatively small differences in
sentencing can result in the large disparities in incarceration rates.
Controlling for effects of transmissibility, susceptibility, and influence
network structure, our model reproduces the observed large disparities in
incarceration rates given the differences in sentence lengths for White and
Black drug offenders in the United States without extensive parameter tuning.
We further establish the suitability of the SIS model as applied to
incarceration, as the observed structural patterns of recidivism are an
emergent property of the model. In fact, our model shows a remarkably close
correspondence with California incarceration data, without requiring any
parameter tuning. This work advances efforts to combine the theories and
methods of epidemiology and criminology.
